Semaglutide side effects: what the evidence actually shows

Most people searching “semaglutide side effects” want two honest things: a realistic picture of what the first weeks feel like, and a clear line between “this is normal” and “this needs a clinician.” Semaglutide — the molecule sold as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for weight management — is one of the best-studied medicines of the last decade, so the common effects are unusually well mapped. The rarer ones are where calm, specific knowledge matters most.

This page describes what semaglutide’s own large trials, its FDA label, and independent peer-reviewed studies report. It describes; it does not prescribe. It contains no doses, no titration schedules, and no instructions — those decisions belong with the prescriber who knows your history.

One caveat before the symptoms: pregnancy and contraception. Semaglutide is not recommended in pregnancy or while breastfeeding. Because rapid weight loss and slowed digestion can affect how the body handles other medicines, anyone who could become pregnant should treat contraception and any plan to conceive as a conversation to have with a prescriber before starting — not after. (The related dual-agonist tirzepatide carries a specific warning that it can make oral contraception less reliable; if you take a pill for birth control, raise this directly.) If you become pregnant or think you might be, contact your prescriber promptly — semaglutide is generally stopped in pregnancy. Because it stays in the body for weeks (long half-life), clinicians typically advise stopping it about two months before trying to conceive.

How common are semaglutide side effects, and when do they start?

The honest headline: side effects are common, but most are mild, temporary, and concentrated in the gut. This sits on the top rung of the evidence ladder — consistent findings across several large randomized trials of the approved drug used for its approved purpose.

In STEP 1, the pivotal obesity trial, gastrointestinal events were the most frequently reported, occurring in roughly three-quarters of people on semaglutide versus about half on placebo. The crucial detail is that they were typically mild-to-moderate and transient. The same broad pattern repeated in SELECT, the very large (~17,600-person) cardiovascular-outcomes trial, where the GI profile was the main driver of side-effect-related stopping — yet most participants stayed on treatment.

Three things are well established about timing:

• They cluster around dose increases. Symptoms tend to appear or worsen when the dose steps up. That is exactly why a slow titration exists — it is a side-effect-management tool, not an arbitrary delay.
• They usually settle. For most people the nausea curve bends down over weeks, not up.
• They are manageable for most, but not all. A minority stop because of GI symptoms — a small single-digit percentage in STEP 1, higher than placebo but far from universal.

What no trial can tell you is which individual you will be. Trials report averages; there is no validated way yet to predict in advance who sails through and who struggles.

Nausea, vomiting, diarrhea, and constipation

These four are the core of the semaglutide experience, and the evidence for them is established. They flow directly from how the drug works: semaglutide slows stomach emptying and acts on appetite centers in the brain, so the gut is fuller for longer and the body is, in effect, being told it is satisfied.

• Nausea is the single most common complaint — usually worst in the days after a dose increase, usually improving as the body adapts.
• Vomiting is less common than nausea but well documented; it becomes a red flag when it is repeated and prevents keeping fluids down (see dehydration, below).
• Diarrhea and constipation both appear on the label — the gut can swing either way, and the same person can experience both at different points.

The label also lists related effects such as abdominal pain, bloating, indigestion (dyspepsia), and decreased appetite — the last of which is the medicine working as designed, not a malfunction. Even so, as the next section explains, appetite suppression that tips into being unable to eat is not something to simply push through.

What is uncertain is the severity distribution outside trial conditions, especially with unsupervised or non-prescription use, where adverse events go largely unrecorded. When you see a precise “X% get nausea” figure attached to grey-market use, treat the confidence as a warning sign, not reassurance.

A note on appetite, eating, and eating disorders

Semaglutide works by turning appetite down, and for most people that is the point. But a personal history of an eating disorder — restriction, binge eating, or anything in between — is worth raising with the prescriber before starting and revisiting during treatment, because a medicine that suppresses hunger can interact with that history in ways worth watching together. Appetite suppression that tips into an inability to eat, or weight loss happening faster than the agreed plan, is something to report — not to push through. None of this is a personal failure and it is not a reason for shame; if eating starts to feel disordered or distressing, reaching out to your clinician or an eating-disorder support service is a sensible, ordinary step to take.

Sulfur burps, reflux, and heartburn

“Sulfur burps” — burps that smell like rotten eggs (hydrogen sulfide) — are one of the most-searched and least-discussed semaglutide complaints. Per the semaglutide prescribing information, eructation (burping), gastroesophageal reflux (GERD), and heartburn are recognized GI effects (they appear among the adverse reactions). The mechanistic story most clinicians give is plausible but not formally proven: because semaglutide slows gastric emptying, food sits longer and can ferment, producing sulfur-smelling gas, and a fuller, slower stomach can push acid upward as reflux.

So the symptom is real and common-enough to be widely reported; the specific sulfur-burp mechanism is best graded emerging/mechanistic, not established. Persistent, severe reflux — or heartburn with trouble swallowing, the feeling of food “sticking,” or black stools — is a reason to seek a clinician’s review rather than to self-manage.

Fatigue

Fatigue is listed on the semaglutide label and is commonly reported, particularly early. The likely contributors are graded plausible rather than proven: eating far less means fewer calories and sometimes lower fluid and electrolyte intake; nausea disrupts sleep and appetite; and rapid weight loss is itself metabolically demanding. Fatigue that is severe, sudden, or paired with dizziness, fainting, a racing heart, or confusion is different — that can signal dehydration or low blood sugar and deserves prompt attention.

Hair loss

Most semaglutide-associated hair loss is telogen effluvium — a diffuse, temporary shedding triggered by the stress of rapid weight loss rather than a direct chemical attack on the follicle. The Wegovy label reports hair loss “associated with weight reduction” (about 3.3% on the drug versus 1% on placebo), and a 2025 scoping review reached the same broad conclusion: the GLP-1 agents linked to the most shedding are simply the ones that produce the most weight loss.

The reassuring part is biological: telogen effluvium does not scar the follicle, so hair typically regrows once weight stabilizes and nutrition recovers — often even if the medicine is continued. Shedding usually starts two to four months after the trigger, which is why it can surface well into treatment. This is graded observational-only: real-world association tied to weight loss, not proven drug toxicity. Patchy loss, scalp redness, scaling, or scarring is a different picture and warrants a clinician (to rule out thyroid, iron, or autoimmune causes). For depth, see our dedicated GLP-1 hair-loss page.

“Ozempic face”

“Ozempic face” — the gaunt, hollowed, or loosened look some people notice after large, fast weight loss — is best understood as volume loss, not a drug toxin. The face stores fat in discrete compartments; lose a lot of weight by any route and the face loses padding, which reads as hollowing and laxity, especially on older or sun-exposed skin. STEP 1’s body-composition substudy confirms semaglutide produces substantial fat loss (alongside some lean-mass loss). This claim is graded supported-but-limited — the underlying physiology is strong, but there is no trial that randomized people to lose the same weight by drug versus diet and then measured faces. It is a cosmetic, not a medical, problem. See our dedicated “Ozempic face” page.

Vision changes and the NAION signal

This is the newest signal that deserves careful, proportionate handling — because it is real, but the evidence is not as strong as headlines imply.

NAION (nonarteritic anterior ischemic optic neuropathy) is a sudden, usually painless loss of vision in one eye from reduced blood flow to the optic nerve. Put the size of the risk first: NAION is rare (regulators estimate up to ~1 in 10,000); within that small baseline, one observational study reported a higher relative rate (hazard ratios ~4.3 and ~7.6) — a signal worth caution, not alarm. Those figures come from a 2024 JAMA Ophthalmology study (Hathaway and colleagues, Harvard), which found semaglutide associated with a higher rate of NAION — about 4.3 in people with type 2 diabetes and about 7.6 in people with overweight/obesity, compared with patients on other medicines. That sounds dramatic, and it prompted regulators to look closely. But the study has important limits: it drew from a single neuro-ophthalmology referral clinic (a population already enriched for eye disease), it is observational, and because NAION is rare in absolute terms, even a large relative risk still translates to a small absolute number of people.

What regulators concluded matters. In June 2025, the EMA’s safety committee (PRAC) reviewed all the data and added NAION to the European product information as a “very rare” side effect — meaning it may affect up to 1 in 10,000 people. As of mid-2026 the US FDA had not added a NAION-specific warning to the US label, which cautions more generally about vision changes; the US label also carries a separate, older warning about diabetic retinopathy complications (from the SUSTAIN-6 diabetes trial, where rapid blood-sugar improvement was linked to worsening retinopathy in some people with pre-existing eye disease).

Honest grade: the NAION link is observational and rare — a genuine safety signal that justifies updated labeling and caution, not a reason for alarm. Sudden vision loss or a new visual blind spot in one eye is a red flag — seek urgent eye care.

Low blood sugar (hypoglycemia)

On its own, semaglutide carries a low risk of dangerous hypoglycemia, because it stimulates insulin mainly when blood sugar is high. The established risk is in combination: the label specifically warns that taking semaglutide with insulin or a sulfonylurea (a common diabetes pill) raises the chance of low blood sugar. This is well documented and is the reason a clinician may adjust other diabetes medicines — a change only they should make. Symptoms of a low — shakiness, sweating, confusion, palpitations, intense hunger — are reasons to seek prompt clinical guidance and to discuss with the prescriber.

Pancreatitis

Acute pancreatitis (inflammation of the pancreas) is an uncommon-but-serious event documented on the semaglutide label as a class precaution. Independent data add nuance: the 2023 JAMA study by Sodhi and colleagues, using a large health-claims database, found GLP-1 use for weight loss associated with a higher rate of pancreatitis compared with an older weight-loss drug. That study is observational — it shows association, not a precise causal rate — but it aligns with the label in justifying vigilance. The practical signal to know: severe, persistent abdominal pain — especially pain that bores through to the back and comes with vomiting — is not a “ride-it-out” symptom. It is a reason to seek prompt clinical evaluation rather than wait.

Thyroid cancer and MEN2 (the boxed warning)

The semaglutide (Wegovy) label carries a boxed warning — the FDA’s most serious — about thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), seen in rodent studies. The honest framing here is important: this is a finding in rats and mice, and whether it translates to humans is not established. Because of the uncertainty, the drug is contraindicated in people with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). A lump in the neck, trouble swallowing, persistent hoarseness, or shortness of breath are the symptoms the label flags for evaluation. Grade: a precautionary, preclinical-rooted warning carried forward into human labeling — taken seriously by regulators precisely because the human risk is unknown rather than known.

Gallstones and gallbladder disease

Gallbladder problems are an established association, and the evidence here is unusually strong because it includes a meta-analysis of randomized trials. The 2022 JAMA Internal Medicine meta-analysis (He and colleagues, 76 RCTs) found GLP-1 use associated with an increased risk of gallbladder and biliary disease — relative risk roughly 1.4, higher at weight-loss doses and with longer treatment. Two mechanisms are at play: the drugs may slow gallbladder emptying, and rapid weight loss itself is a classic, long-known trigger for gallstones. The label lists acute gallbladder disease accordingly. Red flags: pain in the upper-right abdomen, fever, or yellowing of the skin or eyes.

Kidney problems and dehydration

Semaglutide does not directly damage the kidneys — the documented risk is indirect and secondary to dehydration. The label notes reports of acute kidney injury, often in the setting of nausea, vomiting, or diarrhea severe enough to cause volume depletion. The chain is logical and well recognized: prolonged GI losses → dehydration → reduced kidney perfusion. This makes the unglamorous advice — staying hydrated, and not powering through days of vomiting alone — genuinely protective. People taking diuretics (“water pills”), ACE inhibitors or ARBs (common blood-pressure medicines), or NSAIDs (such as ibuprofen) are at higher risk of acute kidney injury during a bout of GI illness; if you take any of these, it is worth asking your clinician in advance whether any of them should be held during severe vomiting or diarrhea — a decision for them to make, not one to take on your own. Signs of dehydration (dizziness, very dark or scant urine, confusion) after prolonged GI symptoms warrant clinical contact.

Muscle and lean-mass loss

When you lose weight, some of what you lose is lean tissue — and semaglutide is no exception. DXA-scan substudies, including the STEP 1 body-composition analysis, confirm that fat mass falls more than lean mass, but some lean mass is lost alongside the larger fat reduction. That part is established. The leap from “lean mass on a scan” to proven loss of real-world strength, function, falls, or fractures is emerging and unproven — the scan number is not the same as a functional outcome, and the long-term significance is still being worked out. The practical, evidence-aligned response is the same one the book develops elsewhere: adequate protein, resistance training, and not losing weight faster than necessary are the levers thought to protect what you keep. See our dedicated GLP-1 muscle-loss page.

Injection-site reactions

For the injectable forms, injection-site reactions — redness, itching, or a small lump — are reported per the semaglutide prescribing information and are generally mild and self-limiting. A genuinely concerning reaction is different: spreading redness with warmth and fever (possible infection), or hives, lip or tongue swelling, or trouble breathing after a dose (a possible allergic reaction, which is a medical emergency).

Gastroparesis, “stomach paralysis,” and the lawsuits

This is the topic most distorted by headlines, so precision matters. Gastroparesis means delayed stomach emptying — and semaglutide deliberately slows gastric emptying as part of how it works. The question is whether it causes severe, persistent gastroparesis (“stomach paralysis”) that outlasts the drug.

What the evidence shows: the 2023 JAMA study (Sodhi) found GLP-1 use for weight loss associated with a higher rate of gastroparesis — hazard ratio about 3.7 versus an older weight-loss drug. That is a real signal, but it is observational, the absolute numbers were small, and it cannot prove the symptoms are permanent. Thousands of product-liability lawsuits (consolidated in US courts) now allege severe gastroparesis and related GI injury; litigation is not evidence of a proven rate or causation — it is a legal process, and its claims have not been adjudicated as scientific fact. Honest grade: observational, with the long-term course genuinely uncertain. Persistent vomiting, a bloated and distended belly, and the feeling that food is not moving are reasons to seek care, not to wait.

At the rarer, more serious end of this same GI spectrum sit ileus and bowel obstruction — the gut slowing or stopping to the point that nothing moves through. The combination to act on is specific: a distended belly + vomiting + not passing stool or gas = urgent. That is an emergency-care situation, not one to wait out.

Mood and mental health

This story has actually moved toward reassurance. After early case reports raised concern about suicidal thoughts, both major regulators investigated. The US FDA (January 2024) reported that its review of trials and observational data did not find evidence that GLP-1 medicines cause suicidal thoughts or actions, while noting it could not entirely rule out a small risk and would keep looking. The EMA reached the same conclusion — no causal association. (In January 2026 the FDA requested that manufacturers remove the precautionary suicidal-behavior-and-ideation warning from GLP-1 labels — a request to update labeling dated Jan 13 2026, not a completed removal.) Grade: the best current evidence is reassuring, not alarming.

The action that goes with that reassurance carries equal weight: mental health is individual, so anyone who notices new or worsening depression, anxiety, or thoughts of self-harm should monitor for it and contact a clinician promptly, regardless of what the population data say — and that monitoring matters most in adolescents and young adults, and in anyone with a psychiatric history.

Alcohol

Two separate things get conflated here. First, drinking less: many people on semaglutide report wanting alcohol less. Early research, including a 2025 randomized trial in alcohol use disorder, is studying this, but it is not an approved use and the evidence is preliminary; this is not a reason to seek the drug for drinking. Second, interaction: alcohol can worsen nausea and, in people on insulin or a sulfonylurea, can contribute to low blood sugar. Separately, heavy alcohol use independently raises the risk of pancreatitis, regardless of semaglutide. There is no established “dangerous direct interaction” between semaglutide and moderate alcohol, but the GI and blood-sugar overlaps — and the independent pancreatitis risk of heavy drinking — are reasons to be cautious and to ask a clinician. See our dedicated GLP-1-and-alcohol page.

Surgery and anaesthesia

This is a practical safety point that is easy to miss. Because semaglutide slows gastric emptying, the stomach may still contain food even after standard pre-operative fasting — which raises the risk of aspiration (stomach contents entering the lungs) under sedation or general anaesthesia. In 2024, the American Society of Anesthesiologists and partner societies issued multi-society guidance on managing GLP-1 users around procedures, balancing aspiration risk against the downsides of stopping the drug. The single most important action is not to make a unilateral decision: tell your surgeon, anaesthetist, and prescriber that you take semaglutide well before any planned procedure, so they can plan fasting and management. Do not stop or change the medicine on your own based on this page.

What happens when you stop (rebound)

Stopping is followed, for most people, by gradual weight regain — and this is established from the trials, not a forum rumor. In the STEP 1 extension, participants regained a large share of lost weight in the year after withdrawal, with metabolic improvements (blood pressure, blood sugar, lipids) drifting back. STEP 4 showed the mirror image: people who switched to placebo regained weight while those who continued kept losing. This reflects the biology of obesity as a chronic, relapsing condition — the medicine manages it while taken rather than curing it. It is not an addiction or a withdrawal syndrome in the classic sense; there is no established physical-dependence crash. How any individual can best maintain, taper, or transition is unsettled and should be planned with a clinician. See our dedicated “stopping GLP-1” page.

Long-term side effects: what we know and don’t

Semaglutide has a multi-year human safety record that most supplements and research peptides can only dream of: SELECT followed ~17,600 people for a mean of about 3.3 years and found a cardiovascular benefit alongside the familiar GI side-effect profile, with no new catastrophic signal emerging at that scale. That is genuinely reassuring for the medium term. What remains unknown is the truly long horizon — effects over a decade or more, effects of starting young and continuing for life, and the real-world rate of rare events (NAION, severe gastroparesis) outside controlled trials. “We don’t have decade-scale data yet” is the honest answer, and anyone claiming certainty in either direction is outrunning the evidence.

Which side effects are serious red flags

Most early discomfort is expected and self-limiting. The following are not “ride-it-out” symptoms — they are reasons to contact a clinician promptly, and for the severe versions, to seek urgent or emergency care:

• Severe, persistent abdominal pain, especially radiating to the back with vomiting — possible pancreatitis.
• Upper-right abdominal pain, fever, or yellowing of the skin/eyes — possible gallbladder disease.
• A bloated, distended belly with vomiting and no bowel movements — possible bowel obstruction or ileus (a distended belly + vomiting + not passing stool or gas = urgent).
• Sudden vision loss or a new blind spot in one eye — possible NAION or other acute eye problem; seek urgent eye care.
• Signs of dehydration (dizziness, very dark or scant urine, confusion) or inability to keep fluids down.
• Symptoms of low blood sugar (shakiness, sweating, confusion) — especially if also on insulin or a sulfonylurea.
• Hives, lip or tongue swelling, or trouble breathing after a dose — possible allergic reaction; this is an emergency.
• A neck lump, persistent hoarseness, or trouble swallowing — the label’s thyroid-warning symptoms.
• New or worsening depression or thoughts of self-harm — contact a clinician regardless of the population data.

Frequently asked questions

How common are semaglutide side effects? Common but mostly mild. In the STEP 1 trial, gastrointestinal effects occurred in roughly three-quarters of people on semaglutide versus about half on placebo, and were typically mild-to-moderate and temporary. Serious events are uncommon. This is established from large randomized trials.

When do semaglutide side effects start, and how long do they last? They tend to appear or worsen right after a dose increase and ease over the following days to weeks as the body adapts. For most people the nausea curve bends down over time. There is no single timeline that fits everyone — trials report averages, not individuals.

What are the most common semaglutide side effects? Nausea, vomiting, diarrhea, and constipation, plus abdominal pain, bloating, indigestion, burping, and reduced appetite. The gastrointestinal cluster dominates, and it is well documented on the FDA label and across the STEP trials.

I’m on semaglutide and might be pregnant — what should I do? If you become pregnant or think you might be, contact your prescriber promptly — semaglutide is generally stopped in pregnancy. Because it stays in the body for weeks (long half-life), clinicians typically advise stopping it about two months before trying to conceive.

Why do I get sulfur or “rotten egg” burps on semaglutide? Burping and reflux are recognized effects. The leading explanation — that slowed stomach emptying lets food ferment and produce sulfur-smelling gas — is mechanistically plausible but not formally proven. Persistent or severe reflux, or trouble swallowing, is worth a clinician’s review.

Does semaglutide cause heartburn and acid reflux? Yes — per the semaglutide prescribing information, GERD and heartburn appear among the adverse reactions, plausibly because a slower, fuller stomach can push acid upward. Most cases are manageable; severe or persistent reflux, or heartburn with food “sticking” or black stools, should be evaluated.

Does semaglutide cause fatigue? Fatigue is listed on the label and is commonly reported early. Likely contributors are eating much less, lower fluid/electrolyte intake, disrupted sleep from nausea, and the metabolic demand of rapid weight loss. Severe fatigue with dizziness, fainting, or palpitations is different and warrants attention.

Is semaglutide hair loss permanent? Usually not. The dominant pattern is telogen effluvium — temporary shedding driven by rapid weight loss, not follicle destruction — so hair typically regrows once weight stabilizes, often even while continuing the medicine. The label ties it to weight reduction (about 3.3% vs 1% on placebo). This is graded observational-only.

Is “Ozempic face” caused by the drug? No — it is volume loss from substantial, fast weight loss. The face loses fat like the rest of the body, which reads as hollowing on older or sun-exposed skin. The same change follows comparable weight loss by any route. It is cosmetic, not a drug toxin.

Can semaglutide cause vision loss or blindness? Rarely. NAION is rare in absolute terms (regulators estimate up to ~1 in 10,000). Within that small baseline, a 2024 JAMA Ophthalmology study reported a higher relative rate of NAION (hazard ratios ~4.3 and ~7.6), and in 2025 the EMA classified NAION as a “very rare” side effect. The evidence is observational and the absolute risk is low — but sudden vision loss in one eye is a red flag needing urgent eye care.

Does semaglutide cause low blood sugar? On its own, rarely, because it stimulates insulin mainly when sugar is high. The real risk is in combination with insulin or a sulfonylurea, which the label specifically warns about. Adjusting those medicines is a clinician’s decision.

Can semaglutide cause pancreatitis? Uncommonly. It is documented on the label as a precaution, and a 2023 JAMA observational study found a higher rate with GLP-1 weight-loss use. Severe abdominal pain radiating to the back with vomiting is a reason to seek prompt clinical evaluation rather than wait. (Heavy alcohol use independently raises pancreatitis risk.)

Does semaglutide cause thyroid cancer? This is unproven in humans. The boxed warning is based on thyroid C-cell tumors in rodents; the human relevance is not established. As a precaution, the drug is contraindicated in people with a personal or family history of medullary thyroid cancer or MEN 2.

Can semaglutide cause gallstones or gallbladder problems? Yes — this is established. A 2022 JAMA Internal Medicine meta-analysis of randomized trials found increased gallbladder and biliary disease risk, driven partly by the drug and partly by rapid weight loss itself. Upper-right abdominal pain, fever, or jaundice are red flags.

Can semaglutide hurt my kidneys? Not directly. The documented risk is acute kidney injury secondary to dehydration from severe vomiting or diarrhea. Staying hydrated and not powering through prolonged GI symptoms is genuinely protective. If you take diuretics, ACE inhibitors/ARBs, or NSAIDs, ask your clinician in advance whether any should be held during severe vomiting or diarrhea — do not self-adjust.

Does semaglutide cause muscle loss? Some lean-mass loss accompanies the larger fat loss on DXA scans — that part is established. Whether it meaningfully reduces real-world strength or function is emerging and unproven. Protein and resistance training are the levers thought to protect muscle.

Is “stomach paralysis” (gastroparesis) a real semaglutide risk? Semaglutide deliberately slows stomach emptying. A 2023 JAMA study found an association with gastroparesis, but it is observational with small absolute numbers, and it cannot prove the symptoms are permanent. Ongoing lawsuits allege severe cases, but litigation is not proof of a rate or cause. At the rarer, more serious end sit ileus and bowel obstruction — a distended belly with vomiting and no stool or gas is urgent.

Does semaglutide affect mental health or cause suicidal thoughts? The best current evidence is reassuring: the FDA (2024) and EMA reviews did not find that GLP-1 medicines cause suicidal thoughts or actions, and in January 2026 the FDA requested removal of the precautionary suicidality label language (a request, not yet a completed removal). Still, anyone noticing new or worsening depression, anxiety, or thoughts of self-harm should monitor for it and contact a clinician promptly — monitoring matters most in adolescents, young adults, and anyone with a psychiatric history.

Can I drink alcohol on semaglutide? There is no established dangerous direct interaction, but alcohol can worsen nausea and contribute to low blood sugar if you also take insulin or a sulfonylurea, and heavy drinking independently raises pancreatitis risk. Separately, many people find they want alcohol less — early research is studying this, but it is preliminary and not an approved use.

Do I need to stop semaglutide before surgery? Possibly, and this is a conversation to have in advance — not a decision to make alone. Because the drug slows stomach emptying, it can raise aspiration risk under anaesthesia. Tell your surgeon, anaesthetist, and prescriber that you take semaglutide so they can plan fasting and management (2024 multi-society guidance).

What happens when I stop semaglutide? Most people gradually regain a large share of lost weight, and metabolic gains fade — shown clearly in the STEP 1 extension and STEP 4. This reflects obesity as a chronic condition, not a withdrawal syndrome. How best to maintain or taper should be planned with a clinician.

What are the long-term side effects of semaglutide? Out to a mean of about 3.3 years (the SELECT trial, ~17,600 people), the profile stayed dominated by GI effects, with a cardiovascular benefit and no new catastrophic signal. Truly long-term, decade-scale effects are not yet known — the honest answer is that the data don’t exist yet.

Which semaglutide side effects are emergencies? Sudden vision loss in one eye; severe abdominal pain (especially radiating to the back) with vomiting; a distended belly with vomiting and no bowel movements or gas; signs of severe dehydration or inability to keep fluids down; severe low blood sugar; and any hives, swelling of the lips/tongue, or trouble breathing after a dose.

Questions to ask a clinician

• What is the plan if nausea or vomiting becomes severe — do I wait, adjust, or call, and how do I reach you?
• Which exact symptoms should prompt me to contact you immediately?
• Given my history, am I at particular risk for gallbladder problems, pancreatitis, or eye disease?
• I have a personal history of an eating disorder — how should we watch for appetite suppression that tips into not eating, or weight loss faster than the plan?
• I take [other medicines] — do any (especially insulin, a sulfonylurea, oral contraception, or diuretics/ACE inhibitors/ARBs/NSAIDs) need attention, and should any be held during severe vomiting or diarrhea?
• How will we protect muscle and nutrition while I lose weight?
• If I could become pregnant: what contraception do you recommend, and how long before trying to conceive should I stop?
• If I become pregnant or think I might be: I understand semaglutide is generally stopped in pregnancy, and that because it stays in the body for weeks, clinicians typically advise stopping it about two months before trying to conceive — what is your specific guidance for me, and how soon should I contact you?
• I have a procedure or surgery coming up — how should we manage the medicine around it?
• What is the maintenance plan, and what would make us pause, change, or stop?

Red flags / when to seek care

The titration phase asks for patience with ordinary discomfort. It does not ask you to ignore the symptoms below. Contact a clinician promptly — and for the severe versions, seek urgent care or your local emergency number — for: severe or persistent abdominal pain (especially radiating to the back with vomiting); upper-right abdominal pain, fever, or yellowing skin or eyes; a bloated, distended belly with vomiting and no bowel movements or gas; sudden vision loss or a new blind spot in one eye; signs of dehydration or inability to keep fluids down; symptoms of low blood sugar; hives, lip or tongue swelling, or trouble breathing after a dose; a neck lump, persistent hoarseness, or trouble swallowing; and new or worsening depression or thoughts of self-harm.

If something feels genuinely wrong in your body, that is not a claim to grade on a ladder — it is a reason to call.