Ozempic carries real risks that range from persistent digestive problems to gallbladder disease, nutrient deficiencies, and significant weight regain if you stop taking it. Some of these side effects are common enough that roughly one in three users experiences them, while others are rare but serious. Here’s what the evidence actually shows.
Digestive Side Effects Are Extremely Common
The most frequent complaint from Ozempic users is gastrointestinal trouble: nausea, vomiting, diarrhea, abdominal pain, and constipation. These aren’t occasional nuisances for a small number of people. In clinical trials, GI side effects hit about 31% of patients on the 1 mg dose and 34% on the 2 mg dose. For comparison, the placebo group reported these problems at far lower rates.
Most people experience these symptoms when they first start the drug or when their dose increases, and the symptoms often improve over weeks to months. But for some, they don’t. Between 3% and 4% of trial participants on Ozempic discontinued the drug specifically because of GI problems, compared to just 0.4% on placebo. Severe gastrointestinal reactions occurred in up to 0.8% of users, which sounds small until you consider the millions of people now taking the drug.
Stomach Paralysis Is a Real Risk
Beyond ordinary nausea, Ozempic and similar drugs have been linked to gastroparesis, a condition where the stomach loses its ability to move food into the small intestine at a normal pace. Symptoms include severe nausea, vomiting, bloating, and abdominal pain that can become debilitating.
A University of British Columbia study that examined insurance records from roughly 16 million U.S. patients found that GLP-1 drugs like Ozempic were associated with a 3.67 times higher risk of gastroparesis compared to another weight loss medication (bupropion-naltrexone). The condition can persist even after stopping the drug in some cases, though more long-term data is still needed on how often that happens.
Gallbladder Problems and Gallstones
Semaglutide, the active ingredient in Ozempic, significantly raises the risk of gallbladder-related problems. A systematic review and meta-analysis found that semaglutide increased the risk of gallbladder disorders by 1.63 times and the risk of gallstones specifically by 2.59 times compared to placebo. Gallstones can cause intense abdominal pain, and in some cases require surgery to remove the gallbladder. Rapid weight loss from any cause is a known trigger for gallstone formation, so this risk likely reflects both the drug’s mechanism and the speed of weight loss it produces.
Thyroid Cancer Warning
Ozempic carries the FDA’s most serious safety label, a boxed warning, for thyroid tumors. In animal studies, semaglutide caused thyroid C-cell tumors, including a type of cancer called medullary thyroid carcinoma (MTC). Whether this translates directly to humans isn’t fully established, but the FDA considers the risk serious enough that Ozempic is completely off-limits for anyone with a personal or family history of MTC or a condition called Multiple Endocrine Neoplasia syndrome type 2.
If you’re taking Ozempic, be aware of symptoms like a lump in your neck, difficulty swallowing, shortness of breath, or persistent hoarseness. These warrant prompt evaluation.
You’ll Likely Regain the Weight If You Stop
One of the most practically important downsides of Ozempic is what happens when you quit. A 2025 systematic review in The BMJ estimated that people regain roughly 0.8 kg (about 1.8 pounds) per month after stopping newer, more potent drugs in this class, which includes semaglutide. Within the first year off the medication, the average regain was about 9.9 kg (nearly 22 pounds).
This means Ozempic isn’t a one-time fix. For most people, maintaining the weight loss requires staying on the drug indefinitely, which raises questions about long-term cost, long-term side effects, and what happens if supply disruptions or insurance changes force you off it.
Nutrient Deficiencies Build Over Time
Because Ozempic works partly by suppressing appetite and slowing digestion, people eat significantly less. That reduced intake creates a real risk of nutritional shortfalls that worsen the longer you stay on the drug.
A large analysis of over 480,000 adults on GLP-1 drugs found that after 12 months of treatment, 13.6% had developed a vitamin D deficiency. Iron deficiency affected 3.2%, B vitamin deficiency hit 2.6%, and 4% developed anemia from poor nutrition. A smaller study that tracked actual food intake found the problem was even more striking: 72% of GLP-1 users consumed less than the recommended amount of calcium, 64% fell short on iron, and only 1.4% met vitamin D recommendations through diet alone.
Researchers have called nutritional deficiencies “a common consequence” of GLP-1 therapy. If you’re on Ozempic, paying attention to nutrient-dense food choices and taking a daily multivitamin (particularly one with vitamin D, iron, and B vitamins) can help offset the gap.
Diabetic Eye Complications
The relationship between Ozempic and eye problems is nuanced. An early clinical trial (SUSTAIN-6) found that semaglutide was associated with a 1.76 times higher rate of diabetic retinopathy complications, including bleeding in the eye and vision changes requiring treatment, compared to placebo. This raised alarm.
However, a much larger retrospective study of over 810,000 semaglutide users found no increased risk of serious diabetic eye disease compared to other diabetes drugs. The current understanding is that when blood sugar drops very rapidly, it can temporarily worsen existing retinopathy. This means the risk is most relevant for people with diabetes who already have eye disease and whose blood sugar improves quickly after starting the drug. It’s less of a concern for people using Ozempic primarily for weight loss without diabetes.
Mental Health Concerns Under Investigation
Reports of mood changes and suicidal thoughts among GLP-1 drug users prompted the Icelandic Medicines Agency to raise a safety signal in July 2023. Both the European Medicines Agency and the U.S. FDA launched investigations. As of the most recent updates, regulatory agencies have not reached definitive conclusions. A large cohort study published in The BMJ specifically looked at suicidality risk among people with type 2 diabetes taking these drugs, and the evidence remains inconclusive.
This doesn’t mean the concern is baseless, but it also doesn’t mean Ozempic causes depression or suicidal thoughts. The rapid body changes, altered relationship with food, and hormonal shifts involved in significant weight loss can all affect mood, making it difficult to isolate the drug’s direct role. If you notice significant mood changes while taking Ozempic, it’s worth bringing up with your provider.
Who Should Not Take Ozempic
Beyond the general risks, certain people should avoid Ozempic entirely. The drug is formally contraindicated for anyone with a personal or family history of medullary thyroid carcinoma, anyone with Multiple Endocrine Neoplasia syndrome type 2, and anyone with a known allergy to semaglutide or its inactive ingredients. People with a history of pancreatitis, severe gastroparesis, or gallbladder disease should discuss these risks carefully before starting, since the drug can aggravate all three conditions.