Orforglipron vs Tirzepatide: Oral Pill vs Injection, Dosing, and Trial Weight Loss

By DoseGauge Editorial · Updated 2026-06-13 · 5 min read

The core difference is the form factor and the receptor target. Orforglipron (sold as Foundayo) is a once-daily oral pill and a single GLP-1 receptor agonist. Tirzepatide (sold as Mounjaro for type 2 diabetes and Zepbound for weight management) is a once-weekly subcutaneous injection and a dual GIP and GLP-1 receptor agonist. Both drugs are made by Eli Lilly. In their respective phase 3 obesity trials, tirzepatide produced a larger average weight loss than orforglipron, while orforglipron offers a pill instead of an injection. That is a factual statement, not a recommendation. A clinician matches a drug and dose to an individual.

Mechanism

Orforglipron is a non-peptide small molecule that activates the GLP-1 receptor. Because it is not a peptide, it survives digestion and can be taken as an oral tablet with no food or water restrictions required. It is a single GLP-1 receptor agonist: it targets one receptor pathway, the same glucagon-like peptide-1 pathway shared by injectable GLP-1 drugs.

Tirzepatide adds a second receptor. It is a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) receptor and the GLP-1 receptor, which is how its FDA label describes it. Both receptor pathways increase glucose-dependent insulin secretion, slow gastric emptying, and reduce appetite. The added GIP-receptor activity is the mechanistic difference between the two drugs.

Pill vs injection, and dosing

The practical difference for most people is the form factor. Orforglipron is a once-daily oral tablet. Tirzepatide is a once-weekly subcutaneous injection administered with an auto-injector pen.

The approved label for orforglipron (Foundayo) describes a monthly titration starting at 0.8 mg daily and stepping up through six strengths to a maximum of 17.2 mg daily. For a full breakdown of those steps, see the orforglipron dosing schedule. The Mounjaro and Zepbound labels for tirzepatide describe a weekly injection starting at 2.5 mg and titrating in 2.5 mg steps to a maximum of 15 mg weekly. The milligram scales are not comparable across the two drugs: the dose of one cannot be converted to the other.

What the trials showed

ATTAIN-1 was a phase 3, randomized, double-blind trial in 3,127 adults with obesity but without diabetes. It studied orforglipron at 6 mg, 12 mg, and 36 mg versus placebo over 72 weeks. The mean change in body weight from baseline was 7.5% at 6 mg, 8.4% at 12 mg, and 11.2% at 36 mg (the treatment-regimen estimand, the trial's primary analysis), versus 2.1% with placebo.

SURMOUNT-1 was a phase 3, randomized, double-blind trial studying tirzepatide at 5 mg, 10 mg, and 15 mg versus placebo over 72 weeks in adults with obesity or overweight with at least one weight-related comorbidity (without diabetes). At the 15 mg dose, the mean body weight reduction was about 20.9% on the same basis.

Three caveats are essential when reading those numbers alongside each other. First, these are entirely separate trials with different populations, protocols, and dose ranges: there is no head-to-head trial comparing the two drugs directly. Second, the ATTAIN-1 doses (6 mg, 12 mg, 36 mg) differ from the approved Foundayo label doses (0.8 to 17.2 mg daily), so the trial figures cannot be treated as the result you would expect on the approved label schedule. Third, trial averages do not predict any individual's outcome, and both trials excluded people with type 2 diabetes.

FAQ

Is orforglipron as effective as tirzepatide?

The trials show different average weight-loss outcomes, with tirzepatide producing a larger average reduction in SURMOUNT-1 (about 20.9% at 15 mg) than orforglipron in ATTAIN-1 (about 11.2% at 36 mg), both over 72 weeks. There is no head-to-head trial, the doses studied differ from approved labels, and trial averages do not predict an individual result. A prescriber weighs efficacy data alongside tolerability, route of administration, cost, and individual factors. For tirzepatide's approved dose steps and titration schedule, see the tirzepatide dosage chart.

Is orforglipron a pill and tirzepatide an injection?

Yes. Orforglipron (Foundayo) is an oral tablet taken once daily. It is a non-peptide small molecule, which means it survives digestion and does not require an injection. Tirzepatide (Mounjaro, Zepbound) is a subcutaneous injection administered once weekly with a pen device.

Are they both made by Eli Lilly?

Yes. Both orforglipron and tirzepatide are Eli Lilly drugs. Orforglipron is sold under the brand name Foundayo, approved for chronic weight management. Tirzepatide is sold as Mounjaro (type 2 diabetes) and Zepbound (weight management and sleep apnea).

Can you switch between them?

Switching between GLP-1 based treatments is a clinical decision. The two drugs have different mechanisms, very different dose scales, and different titration schedules. The approved labels do not provide a conversion or crossover regimen. Any switch would involve re-titration under medical supervision, and the specifics are a conversation for your prescriber.

Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.