Ozempic vs Tirzepatide

Key differences

Ozempic is a product and tirzepatide is an ingredient, and not the one in Ozempic. Ozempic contains semaglutide.¹ Tirzepatide is a separate peptide from a different company, sold under two brand names that carry different labels.²⁶

One hormone receptor or two

Semaglutide is a GLP-1 analogue: it shares 94% of its sequence with human GLP-1, a natural hormone, and selectively activates the GLP-1 receptor.¹ Tirzepatide is a dual agonist: it activates the GLP-1 receptor and also the receptor for GIP (glucose-dependent insulinotropic polypeptide).² Both labels say the drug raises insulin release and lowers glucagon in a glucose-dependent way, and both drugs slow stomach emptying.¹²

The head-to-head trial in type 2 diabetes

SURPASS-2 is the direct comparison. It randomized 1,879 patients with type 2 diabetes not controlled on metformin to tirzepatide 5, 10 or 15 mg or semaglutide 1 mg once weekly for 40 weeks, in an open-label design.⁵² HbA1c fell 2.01, 2.24 and 2.30 percentage points on the three tirzepatide doses, against 1.86 on semaglutide.⁵ Weight fell 1.9, 3.6 and 5.5 kg more on tirzepatide than on semaglutide.⁵

Stomach and gut effects were the most common in both groups, mostly mild to moderate. Nausea affected 17% to 22% on tirzepatide and 18% on semaglutide; diarrhea, 13% to 16% against 12%; vomiting, 6% to 10% against 8%.⁵ Serious adverse events were reported in 5% to 7% on tirzepatide and 3% on semaglutide.⁵ Eli Lilly funded the trial.⁵

Two limits apply. Patients and doctors knew which drug was given, and the semaglutide arm used 1 mg, not Ozempic's top dose of 2 mg.⁵¹ For scale, in Ozempic's own 40-week trial of 961 adults, 2 mg lowered HbA1c by 2.1 points against 1.9 on 1 mg.¹

Weight loss: which brands carry the indication

Neither Ozempic nor Mounjaro is approved for weight loss.¹² Each molecule has a separate brand for that use. Tirzepatide's is Zepbound, first approved on November 8, 2023.⁸ Its label covers long-term weight reduction in adults with obesity, or with overweight plus a weight-related condition.⁶ Semaglutide's is Wegovy.¹²

The obesity head-to-head, SURMOUNT-5, was an open-label trial in 751 adults with obesity but without type 2 diabetes. Each took the highest weekly dose they tolerated of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks.¹⁰⁹ Average weight fell 20.2% on tirzepatide and 13.7% on semaglutide.⁹ Neither semaglutide dose is an Ozempic dose, and Eli Lilly funded this trial too.¹⁹

Dose scale, timing and contraception

Milligram numbers do not carry across the two molecules: Ozempic tops out at 2 mg a week, Mounjaro at 15 mg in adults.¹² Both labels raise the dose in steps of at least 4 weeks to reduce the risk of stomach and gut side effects, and in both the prescriber sets the dose.¹²

Timing rules differ. Semaglutide's half-life is about 1 week and tirzepatide's about 5 days.¹² A missed Ozempic dose can be taken within 5 days, a missed Mounjaro dose within 4 days.¹² Moving the weekly injection day needs more than 48 hours between Ozempic doses and at least 72 hours between Mounjaro doses.¹²

Birth control pills are a label difference. The Mounjaro label says they may work less well and advises switching to a non-oral method, or adding a barrier method, for 4 weeks after starting and after each dose increase.² In one study, a single 5 mg dose cut peak hormone levels from an oral contraceptive by 55% to 66%.² The Ozempic label's advice on oral medicines is general: slower stomach emptying could change their absorption, so it advises caution.¹

Pregnancy, breastfeeding, kidneys and liver

The labels frame pregnancy differently. The Ozempic label says to stop at least 2 months before a planned pregnancy, because semaglutide takes a long time to wash out.¹ The Mounjaro label says human data are too limited to judge the risk. In animal studies, tirzepatide slowed fetal growth, and caused malformations in rats, alongside drug effects on the mothers' weight and food intake.² For breastfeeding, there are no data on semaglutide in human milk.¹ In a study of 11 nursing women given one 5 mg dose of tirzepatide, the drug was undetectable in 164 of 171 milk samples.² Neither label calls for a dose change for kidney or liver impairment.¹²

Safety labels side by side

Both labels carry a boxed warning for thyroid C-cell tumors: each drug caused them in rodents, and whether it does so in people is unknown.¹² Both are ruled out with a personal or family history of medullary thyroid carcinoma or with MEN 2.¹² Both warn about pancreatitis, gallbladder disease, kidney injury from dehydration and low blood sugar when combined with insulin or a sulfonylurea.¹²

Placebo-controlled trials on each label show a similar pattern. Nausea affected 15.8% to 20.3% on Ozempic 0.5 to 1 mg against 6.1% on placebo, and 12% to 18% on Mounjaro 5 to 15 mg against 4%.¹² Those trials enrolled different patients, so only SURPASS-2 compares the two drugs directly. Most of these effects appeared while the dose was being raised.¹²

Ozempic and Mounjaro are prescription only in the US.³⁴ Both injections are supplied as a ready-made solution, with nothing to mix.¹²

Which page to read next

Read the Ozempic profile for its full label and the tirzepatide profile for the molecule and its research record. Tirzepatide's two brands have their own pages: the Mounjaro profile and the Zepbound profile. For the two diabetes brands side by side, see Mounjaro vs Ozempic; for the molecules, see Mounjaro vs semaglutide. Weight results are gathered in tirzepatide and weight loss and Ozempic and weight loss. The GLP-1 comparisons page lists every pair.