Ozempic and Other GLP-1 Injections: What Research Says About Benefits and Risks

Ozempic became a household name. The medicine behind it is not new, and it is not the only injection in this family. Semaglutide, tirzepatide, liraglutide, and dulaglutide are prescription drugs studied for type 2 diabetes, chronic weight management, or both. They can help a lot of the right patients. They also have labeled risks that social media usually skips.

This article summarizes what regulators put on the labels and what large trials actually measured. It is educational, not medical advice. Do not start, stop, or change a dose without the clinician who prescribes it.

Disclosure: SmartEat is a nutrition app. We do not sell or prescribe these drugs. We do help people track protein and fiber when appetite drops, and book a certified nutritionist when the diet is the hard part.

What these injections do

GLP-1 receptor agonists copy a gut hormone that helps the pancreas release insulin when glucose is high, slows how fast the stomach empties, and reduces appetite. Tirzepatide also activates GIP receptors. That is why people eat less without "trying harder" in the usual sense - and why greasy meals, big portions, and skipped protein become a nutrition problem, not a willpower problem.

They are not a vitamin, a detox, or a cosmetic shortcut. In the United States, the Food and Drug Administration (FDA) approves specific brand names for specific uses. Using a diabetes pen for weight loss without that indication is a clinical decision, not a lifestyle hack.

The main brands (same family, different labels)

Brand names are not interchangeable even when the molecule looks similar. Dose, device, and approved use differ. Always match the box to the prescription.

If your clinician named a brand you do not see here, ask them which molecule it is. The risk list below is class-overlapping, with extra notes where labels differ.

What large trials actually showed

These numbers are averages from randomized trials, not a promise for one person. Lifestyle support was part of the protocols.

• STEP 1 (NEJM, 2021): In adults with overweight or obesity, weekly semaglutide 2.4 mg plus lifestyle intervention led to a mean weight change of -14.9% at 68 weeks, versus -2.4% with placebo. A DXA substudy found a greater drop in fat mass than in lean mass - lean tissue still fell, which is why protein and resistance training matter if your clinician says they are safe.
• SELECT (NEJM, 2023): In 17,604 adults with overweight or obesity and existing cardiovascular disease but without diabetes, weekly semaglutide 2.4 mg reduced a composite of cardiovascular death, nonfatal heart attack, or nonfatal stroke by 20% versus placebo (hazard ratio 0.80) over a mean 39.8 months. More people stopped the drug for side effects than stopped placebo (16.6% vs 8.2%), mainly gut symptoms.
• SURMOUNT-1 (NEJM, 2022): In adults with obesity (without diabetes), weekly tirzepatide at 72 weeks produced mean weight change of -15.0% (5 mg), -19.5% (10 mg), and -20.9% (15 mg), versus -3.1% with placebo on the treatment-regimen analysis. Most common side effects were gastrointestinal, usually during dose increases.

Those trials are why clinicians take the class seriously for the right medical indications. They are also why "everyone at the office is on it" is not an indication.

Common side effects (the ones trials see often)

FDA labels for Ozempic list nausea, vomiting, diarrhea, abdominal pain, and constipation as the most common adverse reactions (reported in 5% or more of treated patients in trials). The same gut pattern shows up across Wegovy, Mounjaro, and Zepbound. Symptoms often peak when the dose goes up and ease for many people later. "Often" is not "harmless." Persistent vomiting, inability to keep fluids down, or severe abdominal pain is a reason to contact a clinician the same day - not to wait for the next refill.

Because the stomach empties more slowly, fatty, fried, and very large meals are frequent triggers. Alcohol can hit harder on a small intake. That is a labeled delay of gastric emptying, not a personality flaw.

Serious risks that belong on the consent conversation

The following are on U.S. prescribing information for semaglutide and/or tirzepatide products, or in European regulator updates. They are uncommon compared with nausea. They are not theoretical blog rumors.

• Boxed warning - thyroid C-cell tumors in rodents. GLP-1 and GIP/GLP-1 injectables carry an FDA boxed warning because rodent studies found thyroid C-cell tumors. It is not proven that this happens in humans. These drugs are contraindicated if you or a close family member has had medullary thyroid carcinoma, or if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Report a neck mass, trouble swallowing, shortness of breath, or persistent hoarseness.
• Pancreatitis. Acute pancreatitis has been observed with GLP-1 receptor agonists. Labels say to stop the drug if pancreatitis is suspected and not to restart if it is confirmed. Severe, persistent upper abdominal pain, with or without vomiting, needs urgent care.
• Gallbladder disease. Gallstones and cholecystitis occurred more often on drug than placebo in trials. Rapid weight loss itself raises gallstone risk. Right-upper-abdominal pain, fever, or yellowing of the skin or eyes needs a medical workup.
• Ileus and severe gut slowing. The FDA added ileus (intestinal blockage) to semaglutide labels after postmarketing reports. Wegovy's label also warns about severe gastrointestinal reactions and says it is not recommended in severe gastroparesis. Severe constipation, inability to pass stool or gas, or a swollen, painful abdomen is an emergency pattern - not "the drug is working."
• Kidney injury from dehydration. Vomiting and diarrhea can deplete volume. Labels tell clinicians to watch kidney function when that happens.
• Low blood sugar when combined with insulin or a sulfonylurea. The GLP-1 itself is glucose-dependent; the combination is not automatically safe. Dose changes belong to the prescriber.
• Diabetic retinopathy complications. In a two-year trial in high-risk type 2 diabetes, retinopathy complications were more common with semaglutide (3.0%) than placebo (1.8%), with a larger gap in people who already had retinopathy. Rapid glucose improvement can temporarily worsen retinopathy. Eye history matters before and during treatment.
• NAION (very rare, EMA 2025). The European Medicines Agency concluded that non-arteritic anterior ischemic optic neuropathy is a very rare side effect of semaglutide (Ozempic, Rybelsus, Wegovy) - up to about 1 in 10,000 people. Sudden vision loss needs urgent eye care. If NAION is confirmed, EMA says treatment should stop.
• Aspiration under anesthesia. Because the stomach may still hold food, labels warn about pulmonary aspiration during general anesthesia or deep sedation. Tell the surgical and anesthesia team you are on a GLP-1 before any procedure. Do not invent your own "hold for two weeks" plan unless they give one.
• Pregnancy and planning pregnancy. Animal studies showed reproductive toxicity. Human data are limited. Labels say to discontinue semaglutide at least two months before a planned pregnancy because of the long washout. Do not use these drugs to "get in shape" while trying to conceive.
• Serious allergic reactions (anaphylaxis, angioedema) have been reported. Stop and get emergency care if swelling of the face, tongue, or throat, or trouble breathing starts.

Muscle and bone are not a boxed warning, but they are a real nutrition issue. A share of lost weight can be lean mass. That is why we already published a separate plate guide: What to eat on a GLP-1.

After you stop

Appetite usually returns. In the STEP 1 extension, people who stopped weekly semaglutide after 68 weeks regained a large share of the lost weight over the following year. That is expected pharmacology, not a moral failure. If the plan is a short "reset," ask the prescriber what the off-ramp looks like - food, activity, and follow-up - before the last pen.

Compounded and unapproved copies

The FDA has stated that compounded semaglutide and tirzepatide products are not FDA-approved and do not go through the same premarket review for safety, quality, or effectiveness. The agency has received reports of adverse events after compounded products, including dosing errors when people drew up doses from vials instead of using a labeled pen. Some products have used salt forms of semaglutide that are not the approved active ingredient. After U.S. shortages of tirzepatide and semaglutide were resolved (late 2024 and February 2025), the legal room to copy these drugs narrowed.

Buy only from a licensed pharmacy filling a real prescription. "Research use only," spa pens, and social-media vials are not a clinical trial.

Who should not treat this as a DIY project

Talk to a clinician first - and usually skip internet dosing - if any of this applies: personal or family history of medullary thyroid cancer or MEN 2; past pancreatitis; severe gastrointestinal disease or known gastroparesis; pregnancy, breastfeeding, or plans to conceive soon; type 1 diabetes (these are not insulin); eating-disorder history; or you are already on insulin or a sulfonylurea. Apps cannot clear those questions.

If you are already on a prescribed pen and food intake has collapsed, that is a dietitian conversation as much as a refill conversation. See when to see a dietitian vs a nutrition app and booking a certified nutritionist in the app.

How SmartEat fits

SmartEat will not prescribe Ozempic. It will show what you actually ate when portions look tiny: scan the plate, barcode the yogurt, and watch protein and fiber instead of only the scale. That is the job the drug does not do.

Bottom line

Ozempic and related injections are among the best-studied tools we have for type 2 diabetes and, at the right brand and dose, for chronic weight management and some heart-risk reduction. The evidence is in NEJM-scale trials, not in before-and-after photos. The risks are on the label: gut effects for many people, and uncommon but serious problems involving the pancreas, gallbladder, gut motility, hydration, eyes, anesthesia, and pregnancy. Compounded copies are a separate, less-reviewed market. A licensed prescriber plus a real food plan is the research-based path. A vial from a stranger is not.

Educational only. Not medical advice. Read the patient leaflet that comes with your pen, and use the official label in your country. Report suspected side effects through your national reporting system (in the U.S., FDA MedWatch).

Sources used for this article:

• Ozempic (semaglutide) U.S. prescribing information, DailyMed (revised 2026)
• Wegovy (semaglutide) U.S. prescribing information, DailyMed
• Wilding et al. STEP 1. N Engl J Med. 2021. Mean -14.9% vs -2.4% at 68 weeks.
• Lincoff et al. SELECT. N Engl J Med. 2023. MACE hazard ratio 0.80 in 17,604 adults.
• Jastreboff et al. SURMOUNT-1. N Engl J Med. 2022. Tirzepatide -15.0% / -19.5% / -20.9% vs -3.1% placebo at 72 weeks.
• EMA PRAC, 2025: NAION listed as a very rare side effect of semaglutide medicines.
• FDA communications on compounded (not FDA-approved) semaglutide and tirzepatide products and dosing-error reports.

Related reading:

• What to eat on a GLP-1: protein, fiber, muscle
• When to see a dietitian vs a nutrition app
• Book a certified nutritionist in the app
• Download SmartEat