Tirzepatide vs. semaglutide: what the evidence shows in 2026

Both molecules are lab-made versions of incretins, the hormones your gut releases after a meal. Semaglutide switches on the GLP-1 receptor only. Tirzepatide switches on GLP-1 and GIP receptors, so it is called a dual agonist. The shared effects are slower stomach emptying, more insulin when glucose runs high and quieter hunger signals.

Each molecule is sold under several brands. Tirzepatide is Mounjaro for type 2 diabetes and Zepbound for weight management and obstructive sleep apnea; both start at 2.5 mg weekly and top out at 15 mg. Semaglutide is Ozempic (up to 2 mg weekly) for diabetes and Wegovy (2.4 mg, or 7.2 mg as Wegovy HD since March 2026) for weight. Semaglutide also comes as daily tablets: Rybelsus, Ozempic tablets and the 25 mg Wegovy pill approved in December 2025. No tirzepatide tablet exists.

SURMOUNT-5 is the only randomized trial built to compare the two for weight. It enrolled 751 adults with obesity and no diabetes. Each person took their maximum tolerated dose: tirzepatide 10 or 15 mg, or semaglutide 1.7 or 2.4 mg. At 72 weeks, mean weight change was −20.2% with tirzepatide and −13.7% with semaglutide. Waist size fell 18.4 cm versus 13.0 cm. More tirzepatide users reached losses of 10%, 15%, 20% and 25% (Aronne et al., NEJM 2025). Lilly funded the trial, and it was open-label.

Pooled studies agree on direction. A 2026 meta-analysis in Clinical Obesity combined 10 studies and 41,381 people. It found about 4.3 percentage points more weight loss with tirzepatide and similar rates of stomach side effects. It also found more serious adverse events with tirzepatide (risk ratio 1.83). A second 2026 review of 12 studies reported a similar gap but warned that the studies varied widely.

Heart evidence is uneven. SELECT showed semaglutide 2.4 mg lowered major cardiovascular events by 20% versus placebo in people with heart disease and no diabetes. In type 2 diabetes, SURPASS-CVOT found tirzepatide noninferior to dulaglutide (hazard ratio 0.92). No trial has compared the two on heart outcomes.

Because both act on the same gut and brain signals, the common complaints match: nausea, diarrhea, vomiting and constipation. They tend to peak in the weeks after each dose increase.

The FDA labels show the scale. In Zepbound's weight trials, 25% to 29% of people had nausea, versus 8% on placebo. In Wegovy 2.4 mg trials the figures were 44% versus 16%. Those trials differed in design, so the numbers cannot be ranked against each other. In SURMOUNT-5, fewer tirzepatide users stopped because of stomach effects (2.7% vs 5.6%).

Wegovy HD adds a newer signal. Skin-sensation changes such as burning or tingling (dysesthesia) affected 22% of people on 7.2 mg, per its label. Both molecules carry warnings for pancreatitis, gallbladder disease and low blood sugar with insulin or a sulfonylurea. Both have a boxed warning about thyroid C-cell tumors in rodents. Tirzepatide can make birth-control pills less reliable for 4 weeks after starting and after each increase.

Tirzepatide may fit if weight reduction is the main goal, a weekly injection is acceptable, and the cost works for you. Zepbound is also the version approved for moderate to severe obstructive sleep apnea in adults with obesity.

Semaglutide may fit if you have heart disease without diabetes, since SELECT is the most direct evidence there. It also fits if you want a daily pill instead of an injection. At Temi it is the lower-priced of the two compounded options.

Neither fits if you or a close relative has had medullary thyroid carcinoma, or you have MEN2. Both labels say to stop when pregnancy is recognized. If you have had pancreatitis or have severe gastroparesis, a prescriber needs to weigh that first.

Trial averages describe groups, not individuals, and results within each arm of SURMOUNT-5 spread widely around the mean. Nobody can predict tolerance ahead of time. Compounded tirzepatide and semaglutide are not FDA-approved, which the FDA says means it does not review them for safety, effectiveness or quality. A clinician who knows your history, labs and other medicines should make the call.