The old standard vs the new one
Metformin vs Ozempic
Updated September 28, 2026
The short answer
Ozempic lowers blood sugar more and causes much more weight loss than metformin, but metformin is far cheaper, taken as a pill, and has decades of safety data. For type 2 diabetes, metformin is usually the first medicine tried, and the two are often used together. For weight loss on its own, metformin's effect is modest, typically a few pounds.
Metformin vs Ozempic (semaglutide) at a glance
| Metformin | Ozempic (semaglutide) | |
|---|---|---|
| Drug class | Biguanide | GLP-1 receptor agonist |
| How it works | Reduces sugar made by the liver and improves insulin sensitivity | Mimics GLP-1: boosts insulin when needed, slows digestion, reduces appetite |
| Typical weight loss | A few pounds on average | Several times more; around 15% at the weight-loss dose |
| Effect on A1c | Lowers it by about 1 to 1.5 points | Lowers it by about 1.5 to 1.8 points |
| How you take it | Tablets once or twice daily | One injection a week |
| Heart benefits | Possible, from older studies | Shown to cut cardiovascular events in high-risk patients |
| Common side effects | Diarrhea, stomach upset; low B12 over years | Nausea, diarrhea, constipation, vomiting |
| Cost | Very low; a generic for decades | Much higher |
Why metformin comes first
Metformin has been used for more than 60 years worldwide. It is cheap, taken by mouth, rarely causes low blood sugar on its own, and its long-term safety is well understood. That is why diabetes guidelines have long started with it.
Guidelines have shifted in recent years. For people with heart disease, kidney disease or obesity alongside diabetes, a GLP-1 like semaglutide is now often recommended early, sometimes before or alongside metformin, because of its heart and weight benefits.
Weight loss: not a close contest
In the landmark Diabetes Prevention Program, people taking metformin lost about 2 kg (roughly 4 to 5 lb) on average over nearly three years. It helps, but it is not a weight-loss drug.
Semaglutide at the 2.4 mg weight-loss dose (sold as Wegovy) produced an average loss of 14.9% of body weight over 68 weeks. Ozempic, the diabetes version, tops out at 2 mg and still produces meaningful weight loss in people with type 2 diabetes.
Side effects compared
Both mainly affect the gut. Metformin's diarrhea and stomach upset often settle after a few weeks and are gentler with the extended-release form. Over years, it can lower vitamin B12, so levels should be checked.
Semaglutide commonly causes nausea, especially as the dose steps up. It is not suitable for people with a personal or family history of medullary thyroid cancer or MEN 2, and it carries rare risks of pancreatitis and gallbladder problems.
Using them together
Metformin and semaglutide work through different mechanisms, so they are commonly combined in type 2 diabetes. The combination rarely causes low blood sugar unless insulin or a sulfonylurea is also involved.
Common questions
This comparison is for general information and is not medical advice. Talk to a licensed clinician before starting, stopping or switching any medication.
Not sure which is right for you?
A licensed clinician reviews your history and labs and recommends the option that fits, if any.