Drug facts
Metformin and semaglutide
Quick answer
They are different kinds of drug with different approvals. Metformin is a biguanide approved to improve blood sugar in type 2 diabetes. Semaglutide is a GLP-1 receptor agonist, approved as Ozempic for type 2 diabetes and as Wegovy for weight reduction. Neither metformin nor Ozempic is approved for weight loss. No trial in either label compares the two drugs, but most of Ozempic’s combination trials gave it to people already taking metformin, and the Ozempic label says metformin needs no dose adjustment alongside it.
What each is approved for1
Each label’s own indications section:
| Drug | Approved for |
|---|---|
| Metformin | “An adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus.” |
| Ozempic (semaglutide) | As an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes; to reduce the risk of major cardiovascular events in adults with type 2 diabetes and established cardiovascular disease; and to reduce the risk of sustained decline in kidney function (eGFR), end-stage kidney disease and cardiovascular death in adults with type 2 diabetes and chronic kidney disease. |
| Wegovy (semaglutide) | Reducing the risk of major adverse cardiovascular events in adults with established cardiovascular disease and either obesity or overweight; reducing excess body weight and maintaining weight reduction long term; noncirrhotic MASH with moderate to advanced liver fibrosis, under accelerated approval. |
The metformin label has one indication, and weight is not part of it2. The word “weight” appears nine times in that label. Three describe dosing, chemistry or a pharmacokinetic comparison, and six report mean body weight beneath trial tables. None describes a use.
Not the same kind of drug2
The metformin label says it lowers blood sugar by decreasing the liver’s glucose production, decreasing the absorption of glucose from the gut, and improving insulin sensitivity, and that insulin secretion “remains unchanged.”
The Ozempic label describes semaglutide as a GLP-1 receptor agonist that stimulates insulin secretion and lowers glucagon secretion in a glucose-dependent way, meaning when blood sugar is high. It says the effect also involves “a minor delay in gastric emptying in the early postprandial phase”1. The Wegovy label adds that GLP-1 is a regulator of appetite and calorie intake3. How semaglutide works →
What happened to weight in each label2
The metformin label reports body weight beneath two adult trials of 29 weeks. Against placebo, mean weight fell 1.4 lb on metformin and 2.4 lb on placebo. In a trial against glyburide, the metformin-only arm lost 8.4 lb, against 0.7 lb on glyburide and a 0.9 lb gain on the two combined.
The Ozempic label’s placebo-controlled trial of semaglutide on its own ran 30 weeks in adults with type 2 diabetes. Mean weight fell 3.8 kg at 0.5 mg and 4.7 kg at 1 mg, against 1.2 kg on placebo4.
Those are different trials in different people, behind approvals 22 years apart (the labels give 1995 for metformin and 2017 for Ozempic). They are not a comparison of the two drugs, and neither label offers one. Weight reduction at 2.4 mg is the subject of STEP 1, which is a Wegovy trial in people without diabetes.
Ozempic was mostly tested on top of metformin4
Section 14.1 of the Ozempic label describes its combination trials by background treatment, and four of them were run in people already taking metformin. The label identifies them by registry number. The trial names below come from the published papers matched to those numbers5, and the figures are the label’s.
| Trial | Weeks | Background | Compared with | HbA1c | Weight |
|---|---|---|---|---|---|
| SUSTAIN 2 | 56 | Metformin (94%) and/or a thiazolidinedione (6%) | Sitagliptin 100 mg daily | −1.3 and −1.5 against −0.7 | −4.2 and −5.5 kg against −1.7 kg |
| SUSTAIN 3 | 56, open-label | Metformin alone (49%), metformin with a sulfonylurea (45%), other (6%) | Exenatide extended-release 2 mg weekly | −1.4 against −0.9 (1 mg only) | −4.8 kg against −2 kg |
| SUSTAIN 4 | 30, open-label | Metformin (48%) or metformin with a sulfonylurea (51%) | Insulin glargine daily | −1.2 and −1.5 against −0.9 | −3.2 and −4.7 kg against +0.9 kg |
| SUSTAIN FORTE | 40 | Metformin, with or without a sulfonylurea | Ozempic 2 mg against 1 mg | −2.1 (2 mg) against −1.9 (1 mg) | −6.4 against −5.6 kg, not a statistically significant difference |
A fifth trial added Ozempic to basal insulin, with or without metformin. In every one, Ozempic was compared with something else while the background treatment continued. None tested metformin itself. The same design runs through SUSTAIN 7, the head-to-head with dulaglutide, which enrolled adults on metformin alone. That trial is not described in the Ozempic label.
Taking both: what the labels say6
The Ozempic label includes metformin in its drug-interaction studies. Metformin’s blood levels were measured at steady-state exposure to semaglutide 1 mg, and the label’s recommendation is “no dose adjustment.” The Wegovy label, describing studies with the semaglutide tablet, lists metformin among the drugs whose levels showed no clinically significant change3.
The Ozempic label’s low-blood-sugar warning names two kinds of medicine: insulin secretagogues such as sulfonylureas, and insulin. Neither section 5.5 nor section 7.1 names metformin. The metformin label’s own warning is built the same way: it says metformin may raise the risk of low blood sugar when combined with insulin or an insulin secretagogue2. The metformin label does not mention GLP-1 drugs or semaglutide at all. Semaglutide’s interaction sections →
Both drugs list digestive reactions among their most common. The metformin label reports diarrhea in 53% against 12% on placebo, and nausea or vomiting in 26% against 8%. Ozempic’s rates are on the diarrhea page. Neither label reports a separate rate for the two taken together. For its 40-week trial of 1 mg and 2 mg added to metformin, with or without a sulfonylurea, the Ozempic label says no new safety signals were identified.
What none of this covers
On the label — Wegovy / Ozempic
The trials above tested the approved Ozempic pen, at fixed doses, in adults with type 2 diabetes, nearly all of them already taking metformin.
In a compounded vial
No compounded preparation has run a trial, with metformin or without it. The figures above describe the approved pen in type 2 diabetes, and none of them was measured on a compounded vial. Compounded semaglutide against Ozempic →
Nothing here is medical advice. Whether to take either drug, or both, and at what dose, is a prescriber’s decision, and this page takes no view on it. It reports what the approved labels say. See the medical disclaimer.
Sources
- FDA prescribing information for OZEMPIC (semaglutide) injection, sections 1 and 12.1, revision 5/2026 DailyMed
- FDA prescribing information for metformin hydrochloride tablets (generic listing on DailyMed, setid 64f5b140-7ad8-4c07-bbfc-ae4618afa850), sections 1, 5.3, 6.1, 7, 12.1 and 14.1, effective 9/2026
- FDA prescribing information for WEGOVY (semaglutide), sections 1, 12.1 and 12.3, revision 6/2026 DailyMed
- FDA prescribing information for OZEMPIC (semaglutide) injection, section 14.1, revision 5/2026 DailyMed
- Trial names matched to the label's registry numbers through PubMed: SUSTAIN 2, Ahrén B, et al. Lancet Diabetes Endocrinol. 2017;5(5):341-354, PMID 28385659; SUSTAIN 3, Ahmann AJ, et al. Diabetes Care. 2018;41(2):258-266, PMID 29246950; SUSTAIN 4, Aroda VR, et al. Lancet Diabetes Endocrinol. 2017;5(5):355-366, PMID 28344112; SUSTAIN FORTE, Frías JP, et al. Lancet Diabetes Endocrinol. 2021;9(9):563-574, PMID 34293304 PubMed
- FDA prescribing information for OZEMPIC (semaglutide) injection, sections 5.5, 6.1, 7.1 and 12.3, revision 5/2026 DailyMed