Short answer
In the main trial, 15 mg produced the most weight loss on average, but only slightly more than 10 mg. At 72 weeks, people lost 15.0% of body weight on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg, against 3.1% on placebo. Vomiting and diarrhea rose with dose. Your prescriber picks the dose that works and that you tolerate.
Source: SURMOUNT-1 (Zepbound label, revised 08/2026)
Average weight loss by dose
SURMOUNT-1 assigned 2,539 adults without diabetes to a fixed weekly dose of 5 mg, 10 mg or 15 mg, or to placebo, for 72 weeks. Everyone also got diet and activity counseling. Average weight loss was 15.0% on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg, against 3.1% on placebo. So the step from 5 mg to 10 mg added 4.5 points on average, and the step from 10 mg to 15 mg added 1.4. The label reports each dose against placebo. It does not report a statistical test of one dose against another.
How many people reached 5%, 15% and 20%
The share of people who lost at least 5% of body weight was 85.1% on 5 mg, 88.9% on 10 mg and 90.9% on 15 mg, against 34.5% on placebo. The gaps widened at bigger targets. At least 15% was reached by 48.0%, 66.6% and 70.6%, against 8.8% on placebo. At least 20% was reached by 30.0%, 50.1% and 56.7%, against 3.1%. In SURMOUNT-2, adults with type 2 diabetes lost 12.8% on 10 mg and 14.7% on 15 mg, against 3.2% on placebo.
Side effects rise with dose
The label pools both trials. Nausea was reported by 25% on 5 mg, 29% on 10 mg and 28% on 15 mg, against 8% on placebo. Vomiting rose from 8% to 11% to 13%, against 2%, and diarrhea from 19% to 21% to 23%, against 8%. Severe stomach and bowel reactions were 1.7%, 2.5% and 3.1%, against 1%. The share who stopped the drug because of side effects was 4.8%, 6.3% and 6.7%, against 3.4%. Constipation ran the other way, highest on 5 mg.
Who decides the dose
The label approves 5 mg, 10 mg or 15 mg once a week as maintenance doses for weight reduction, with 15 mg as the maximum. Everyone starts at 2.5 mg for 4 weeks, and increases come in 2.5 mg steps after at least 4 weeks on each dose. The label tells prescribers to consider treatment response and tolerability when choosing the maintenance dose, and a lower one if a dose is not tolerated. Trial averages cannot tell you which dose fits you. That is your prescriber's call.
Related questions
Is 15 mg always better than 10 mg?
Not for everyone. On average 15 mg gave 20.9% weight loss against 19.5% on 10 mg in SURMOUNT-1, and vomiting and diarrhea were somewhat more common on 15 mg.
Can you stay on 5 mg?
Yes, if your prescriber decides it. The label lists 5 mg as an approved maintenance dose for weight reduction, and people on 5 mg lost 15.0% on average in SURMOUNT-1.
Is 2.5 mg an effective dose?
The label says the 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage.
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Published 2026-10-07 · Last checked 2026-10-07
Educational content, not medical advice. Made for the United States.