Side effects
What these drugs do to your body, what the label says, and what to do about it.
The cheapest GLP-1 we track today is $69/mo at SnagRx, checked October 2026. Every GLP-1 price
Side effectsGLP-1s and birth control: which ones weaken the pill, for how long, and what to use insteadTirzepatide (Zepbound, Mounjaro) and orforglipron (Foundayo) can make the birth control pill less reliable, so their labels say to switch to a non-oral method or add a condom for 4 weeks (30 days for Foundayo) after starting and after every dose increase. Semaglutide (Ozempic, Wegovy, Rybelsus) carries no such rule: its label studies showed no clinically significant change in pill hormones. The patch, ring, shot, implant and IUD are not affected by any of them.Side effectsGLP-1 muscle loss: how much of the weight is muscle, and what protects itOn semaglutide or tirzepatide, roughly a quarter to two fifths of the weight you lose is lean mass rather than fat: 25% in tirzepatide's SURMOUNT-1 scan substudy, and 25% to 39% across 20 randomised trials. That share is close to what diet-only weight loss costs. Lean mass is not all muscle, and strength held up in the shorter trials. Resistance training cut the lean share to 17.5% in the pooled trials, and expert groups pair it with enough protein.Side effectsWhat is “Ozempic face”? What the studies show, who gets it, and what fixing it costs“Ozempic face” is the hollow, older look a face can take on after fast, large weight loss. It is not a listed side effect: facial fat leaves with fat everywhere else. The first CT study found a median 9% loss of midface volume after an average 11 kg lost, about 7% per 10 kg, mostly in the fat just under the skin. Age, how much and how fast you lose, and regain shape how much it shows. Plastic surgeons put the average for hyaluronic acid filler at $715.Side effectsOzempic side effects, and the ones that actually make people stopThe common Ozempic side effects are gastrointestinal: nausea, vomiting, diarrhoea and constipation. They cluster in the first weeks and after each dose increase, which is why the drug is titrated slowly rather than started at the dose that does the work. Ozempic also carries a boxed warning for thyroid C-cell tumour risk, and the label for Wegovy, the same molecule, advises against combining it with another GLP-1. The practical thing nobody tells you: most people who quit do it during titration, and what decides whether that costs them money is the seller's pause and refund terms, not the sticker price.Side effectsWegovy side effects, and why the top of the ladder is differentWegovy's side effects are semaglutide's side effects: nausea, vomiting, diarrhoea and constipation, worst in the first weeks and after each dose increase. What makes Wegovy different from Ozempic is not the molecule but the destination. Wegovy is dosed for weight management, climbing to 2.4 mg with a 7.2 mg high-dose strength above it, and dose is the main driver of how pronounced the gastrointestinal effects get. It also carries a boxed warning for thyroid C-cell tumour risk. One useful fact while you decide whether to push through: Novo's self-pay price is flat across every pen dose, so a slower climb costs a brand patient nothing.Side effectsSemaglutide side effects, and what compounding does and does not changeSemaglutide's side effects are gastrointestinal: nausea, vomiting, diarrhoea and constipation, worst early and after each dose increase. Those belong to the molecule, so they are the same whether it came in a Novo Nordisk pen or a compounding pharmacy's vial. What compounding changes is everything around the molecule. A compounded drug is not FDA-approved, so the finished product has not been reviewed for safety, effectiveness or manufacturing quality, and the FDA has said the enforcement discretion that allowed 503A pharmacies to compound semaglutide has ended. It also usually arrives as a vial and a syringe rather than a pre-set pen, which moves dose measurement to you.Side effects“Ozempic butt” is not a side effect either“Ozempic butt” describes loss of volume and sagging skin around the buttocks after fast weight loss. Like “Ozempic face”, it is not a listed adverse effect and not something the drug does to that area specifically. Fat leaves everywhere when you lose fat, including where you would rather it stayed, and skin that loses volume quickly does not always retract to match. It follows large rapid weight loss from any cause. The two things you influence are how fast you lose and whether you can afford to stay on a steady dose instead of stopping and rebounding.Side effectsGLP-1 hair loss: what is actually going onHair shedding on a GLP-1 is real, and the labels now count it: 3.3% of people on Wegovy 2.4 mg and 5.8% on 7.2 mg, against 1% on placebo, most of them women. Wegovy's and Zepbound's labels both say it was associated with weight reduction. Rapid weight loss is a long-recognised trigger for a temporary shedding phase, after bariatric surgery and crash dieting too. Two things make it more likely: how fast you are losing, and whether you eat enough protein and micronutrients.Side effectsGLP-1s and alcohol: what is known and what is notThere is no blanket instruction on the label saying not to drink on a GLP-1. The specific risk that is well established is low blood sugar, and it applies to people who also take insulin or a sulfonylurea, where alcohol can compound the effect. Beyond that, two things are widely reported and not settled: that alcohol tolerance changes, and that interest in drinking drops. Both are worth mentioning to a prescriber and neither is something a website should turn into advice.Side effectsMounjaro side effects: the label's numbers by dose, the low blood sugar risk, and how tirzepatide compares at weight-loss dosesOn Mounjaro's own label, the common side effects are stomach ones and they rise with the dose: nausea in 12, 15 and 18 percent of people at 5, 10 and 15 mg against 4 percent on placebo, diarrhea 12 to 17 against 9, and any gastrointestinal reaction in 37 to 44 percent against 20. Most of it happens while the dose is being raised and fades. Low blood sugar is rare on Mounjaro alone and is mainly a risk when it is added to insulin or a sulfonylurea. Below: the full table, the rare warnings, and why Zepbound's numbers for the same molecule look higher.Side effectsThe GLP-1 diet: what to eat on Ozempic, Wegovy or Zepbound, and what to limit, from the 2025 joint advisoryThere is no special GLP-1 diet, but there is now a consensus on how to eat on one. A 2025 advisory from four medical societies says to build meals around fruits, vegetables, whole grains, legumes, lean proteins, nuts and seeds; limit refined carbohydrates, sugary drinks, red and processed meats, fast food and ultra-processed snacks; eat small regular meals; drink enough fluids; and put protein first, because appetite drops and muscle is at risk. During dose increases, smaller meals and avoiding fatty or high-fibre foods ease nausea.Side effectsGLP-1 constipation, nausea, diarrhoea and fatigue: the label numbers, and what the labels say to doThe four gut effects are the four most common side effects of every GLP-1, and the labels put numbers on them. On Wegovy 2.4 mg: nausea 44%, diarrhoea 30%, constipation 24%, vomiting 24%, fatigue 11%, against 16%, 16%, 11%, 6% and 5% on placebo. On Zepbound at 15 mg: nausea 28%, diarrhoea 23%, constipation 11%, vomiting 13%, fatigue 7%. They cluster around dose increases, they are the reason 6.8% of Wegovy patients and up to 6.7% of Zepbound patients stopped, and both labels prescribe the same fix: climb slower.Side effectsZepbound side effects: the label's table by dose, who actually quits, and how it compares to semaglutideZepbound's label puts a number on every common side effect at each of its three maintenance doses. Nausea runs 25 to 29 percent against 8 on placebo, diarrhoea 19 to 23, vomiting 8 to 13, constipation 11 to 17. Across the two approval trials, 4.8 to 6.7 percent of people stopped the drug because of side effects, against 3.4 percent on placebo, and most of those who quit did so in the first months, from gut effects during dose escalation. Below that table are the rarer things the label warns about, with the trial rates where it gives them, and the honest comparison to Ozempic's table.
