Separate trials, not a head-to-headWe found no published trial that randomized people to Foundayo or Zepbound from the start. The figures below come from each drug's own trials and labels, which differ in design. The choice of medicine is a prescriber's decision.
Foundayo vs Zepbound at a glance
Foundayo is a once-daily tablet and Zepbound a once-weekly injection; both are made by Eli Lilly and approved for long-term weight reduction.[1][2]
| Foundayo | Zepbound | |
|---|---|---|
| Drug | Orforglipron, a small-molecule (non-peptide) GLP-1 receptor agonist | Tirzepatide, a peptide acting on GIP and GLP-1 receptors |
| Form | Tablet by mouth | Injection under the skin (pen, vial, KwikPen) |
| How often | Once daily | Once weekly |
| Starting dose | 0.8 mg | 2.5 mg |
| Highest dose | 17.2 mg | 15 mg |
| Time between dose steps | At least 30 days | At least 4 weeks |
| Food | With or without food; no water rules | Any time of day, with or without meals |
| Half-life | About 29 to 49 hours | About 5 days |
| FDA approval for weight | April 1, 2026 | November 8, 2023 |
| Other approved use | None (weight only) | Obstructive sleep apnea in adults with obesity |
Sources: Foundayo label and FDA announcement; Zepbound label.[1][3][4][2] Lilly describes Foundayo as a pill that “can be taken any time of day without food or water restrictions.”[4]
Orforglipron vs tirzepatide: how the drugs differ
Orforglipron is a small, non-peptide molecule that acts only on the GLP-1 receptor, while tirzepatide is a large peptide that acts on both the GIP and GLP-1 receptors.[3][2] That difference explains the route: orforglipron is absorbed from the gut (77% bioavailability after a 0.8 mg dose), while tirzepatide is injected (80% bioavailability under the skin).[1][2] Foundayo is not a pill form of tirzepatide; why no tirzepatide tablet exists is covered on tirzepatide pills.
Foundayo vs Zepbound weight loss in the trials
Zepbound produced roughly twice the average weight loss of Foundayo in each drug's own 72-week trial: −20.9% on Zepbound 15 mg against −11.1% on Foundayo 17.2 mg, each compared with its own placebo group.[7][1]
| Trial (length) | Who | Placebo | Low dose | Middle dose | Top dose |
|---|---|---|---|---|---|
| Foundayo Trial 1 (72 weeks)[1] | Obesity, no diabetes | −2.1% | −7.4% (5.5 mg) | −8.3% (9 mg) | −11.1% (17.2 mg) |
| SURMOUNT-1, Zepbound (72 weeks)[7] | Obesity, no diabetes | −3.1% | −15% (5 mg) | −19.5% (10 mg) | −20.9% (15 mg) |
| Foundayo Trial 2[1] | Obesity with type 2 diabetes | −2.5% | −5.1% (5.5 mg) | −7.0% (9 mg) | −9.6% (17.2 mg) |
| SURMOUNT-2, Zepbound (72 weeks)[8][2] | Obesity with type 2 diabetes | −3.2% | — | −12.8% (10 mg) | −14.7% (15 mg) |
The Foundayo label presents its trials at “equivalent dosages” of the marketed tablets.[1] Because the trials enrolled different people, the gap between drugs is a rough guide, not a measured difference. Zepbound's dose-by-dose results are on tirzepatide for weight loss.
Side effects compared
Both drugs mainly cause stomach side effects, and in the label tables vomiting and constipation were more frequent on Foundayo, and slightly more people stopped Foundayo because of side effects.[1][2]
| Side effect | Foundayo 5.5–17.2 mg | Placebo | Zepbound 5–15 mg | Placebo |
|---|---|---|---|---|
| Nausea | 26–35% | 10% | 25–29% | 8% |
| Diarrhea | 21–25% | 11% | 19–23% | 8% |
| Vomiting | 13–24% | 4% | 8–13% | 2% |
| Constipation | 20–27% | 9% | 11–17% | 5% |
| Abdominal pain | 13–14% | 7% | 9–10% | 5% |
| Dyspepsia | 12–16% | 4% | 9–10% | 4% |
| Fatigue | 6–9% | 4% | 5–7% | 3% |
| Eructation (burping) | 6–8% | 1% | 4–5% | 1% |
| Hair loss | 4–5% | 2% | 4–5% | 1% |
| Headache | 8–9% | 7% | Not in the table | — |
| Stopped for side effects | 6–10% | 3% | 4.8–6.7% | 3.4% |
Both labels carry a boxed warning about thyroid C-cell tumors. Tirzepatide caused them in rats; the Foundayo label notes that orforglipron “is not pharmacologically active in rats or mice and did not produce tumors in rodents.”[2][1] Both are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2. Zepbound's full table is on Zepbound side effects.
Missed doses, birth control and interactions
The two labels differ most on missed doses, oral contraceptives and drug interactions.[1][2]
- Missed dose: Foundayo is taken as soon as possible without doubling up; after 7 or more missed days in a row, the label says to restart escalation at a lower dose. Zepbound can be taken within 4 days of a missed dose, otherwise skipped. See missed Zepbound dose.
- Birth control pills: Foundayo's label asks for a non-oral or added barrier method for 30 days after starting and after each dose increase; Zepbound's asks for 4 weeks after starting and after each increase.
- Interactions: Foundayo is broken down mainly by CYP3A4, so strong CYP3A4 inhibitors cap it at 9 mg a day, strong inducers should be avoided, and simvastatin should not exceed 20 mg a day. The Zepbound label's interaction advice is about oral medicines affected by slower stomach emptying, birth control pills, and low blood sugar with insulin or sulfonylureas.
- Not together: Foundayo's label says not to use it with another GLP-1 receptor agonist.
Switching from Zepbound to Foundayo
Switching from Zepbound to Foundayo kept most of the earlier weight loss in a 52-week trial: people kept 74.7% of their prior loss on Foundayo versus 49.2% on placebo.[9]
| Measure | Foundayo | Placebo |
|---|---|---|
| Share of prior weight loss kept at week 52 (Nature Medicine)[9] | 74.7% | 49.2% |
| Same endpoint, Lilly's primary analysis[10] | 78.0% | — |
| Weight at switch → week 52[10] | 90.9 kg → 95.9 kg | — |
The authors note the trial had no group that simply stayed on the injection.[9] In a separate trial reported the same day, staying on the full Zepbound dose kept weight at 89.5 → 88.7 kg, while stepping down to 5 mg regained 5.6 kg on average.[10] The labels give no dose conversion between the two drugs.[1][2]
Foundayo vs Zepbound cost
At Lilly's self-pay prices, Foundayo costs $149 to $299 per 30 days and Zepbound $299 to $449 per 4 weeks with on-time refills.[5][6]
| Foundayo dose | Per 30 days | Per day | Zepbound dose | Per 4 weeks | Per day |
|---|---|---|---|---|---|
| 0.8 mg | $149 | $4.97 | 2.5 mg | $299 | $10.68 |
| 2.5 mg | $149* | $4.97 | 5 mg | $399 | $14.25 |
| 5.5 mg | $199* | $6.63 | 7.5 mg | $449† | $16.04 |
| 9 mg | $299 | $9.97 | 10 mg | $449† | $16.04 |
| 14.5 mg | $299† | $9.97 | 12.5 mg | $449† | $16.04 |
| 17.2 mg | $299† | $9.97 | 15 mg | $449† | $16.04 |
* Foundayo 2.5 and 5.5 mg prices are “temporarily reduced through December 31, 2026.” † Applies when refilled on time (within 45 days); Zepbound's regular prices are higher.[5][6] Per day = price ÷ 30 or ÷ 28. Both drugs are in the Medicare GLP-1 Bridge, Foundayo in all forms and Zepbound as the KwikPen only; see Zepbound insurance coverage.[11]
First-year cost on each label schedule
At today's self-pay prices, the first year at the fastest label escalation comes to $3,188 for Foundayo (12 fills of 30 days) and $5,637 for Zepbound (13 fills of 4 weeks).[5][6]
| Fill | Foundayo dose | Price | Zepbound dose | Price |
|---|---|---|---|---|
| 1 | 0.8 mg | $149 | 2.5 mg | $299 |
| 2 | 2.5 mg | $149 | 5 mg | $399 |
| 3 | 5.5 mg | $199 | 7.5 mg | $449 |
| 4 | 9 mg | $299 | 10 mg | $449 |
| 5 | 14.5 mg | $299 | 12.5 mg | $449 |
| 6 | 17.2 mg | $299 | 15 mg | $449 |
| 7 | 17.2 mg | $299 | 15 mg | $449 |
| 8 | 17.2 mg | $299 | 15 mg | $449 |
| 9 | 17.2 mg | $299 | 15 mg | $449 |
| 10 | 17.2 mg | $299 | 15 mg | $449 |
| 11 | 17.2 mg | $299 | 15 mg | $449 |
| 12 | 17.2 mg | $299 | 15 mg | $449 |
| 13 | — | — | 15 mg | $449 |
| Total | 360 days | $3,188 | 364 days | $5,637 |
Assumptions: every step taken at the earliest point the label allows (30 days for Foundayo, 4 weeks for Zepbound), the top dose kept after that, and every refill on time. Foundayo's 2.5 and 5.5 mg prices are temporary until December 31, 2026, and the label leaves the dose to the prescriber, so a real year may cost more or less.[1][2][5]
Related
- Zepbound vs WegovyIncluding the Wegovy pill
- Zepbound costPer dose, per mg and per year
- Tirzepatide dosage chartThe weekly dose steps
Frequently asked questions
Is Foundayo as effective as Zepbound?
Is Foundayo the same as Zepbound in pill form?
Can you switch from Zepbound to Foundayo?
In the ATTAIN-MAINTAIN trial, people who switched from Zepbound kept 74.7% of their earlier weight loss on Foundayo versus 49.2% on placebo after 52 weeks. Switching is a prescriber's decision.[9]
Is Foundayo cheaper than Zepbound?
Sources
- Foundayo (orforglipron) tablets: prescribing information
- Zepbound (tirzepatide) injection: prescribing information, Medication Guide and Instructions for Use
- FDA approves first new molecular entity under National Priority Voucher program (Foundayo)
- FDA approves Lilly's Foundayo (orforglipron)
- Foundayo on LillyDirect: self-pay prices
- Zepbound on LillyDirect: formats and self-pay prices
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)
- Garvey WT et al. Tirzepatide once weekly for obesity in type 2 diabetes (SURMOUNT-2)
- Aronne LJ et al. Orforglipron for maintenance of body weight reduction (ATTAIN-MAINTAIN)
- Lilly's Foundayo and lower-dose Zepbound helped people maintain weight loss after switching from higher doses
- Medicare GLP-1 Bridge: information for providers