FDA approved Foundayo on April 1, 2026, as a once-daily pill for weight reduction and long-term maintenance [3]. Because Lilly also makes Zepbound, many people assume the pill is a tablet form of the same drug. It isn't, and the trial results show the difference.
Two different Lilly drugs
Foundayo contains orforglipron, a small, non-peptide molecule designed to be taken by mouth [4]. Its label describes it as a GLP-1 receptor agonist, with no second receptor target [1]. Zepbound contains tirzepatide, a peptide built to hit both the GIP and GLP-1 receptors, and it has to be injected [2]. Different molecule, different targets, different form. The Zepbound guide covers the injection in depth.
Zepbound's trial showed about twice the weight loss
| Foundayo (orforglipron) | Zepbound (tirzepatide) | |
|---|---|---|
| Molecule | Small molecule, GLP-1 only | Peptide, GIP and GLP-1 |
| Form | Tablet once a day | Injection once a week |
| Main obesity trial | ATTAIN-1: 3,127 adults, 72 weeks; −7.5%, −8.4% and −11.2% on the three trial doses vs −2.1% placebo [4] | SURMOUNT-1: 2,539 adults, 72 weeks; −15.0%, −19.5% and −20.9% vs −3.1% placebo [6] |
| Share losing a lot of weight (top dose) | 54.6% lost 10% or more; 18.4% lost 20% or more [4] | 57% lost 20% or more [6] |
| Stopped for side effects | 5.3% to 10.3% vs 2.7% on placebo | 4.3% to 7.1% vs 2.6% on placebo |
| Maintenance data | ATTAIN-MAINTAIN: kept 74.7% of loss after switching from tirzepatide, vs 49.2% on placebo [5] | SURMOUNT-4: staying on it, weight fell another 5.5%; switching to placebo, it rose 14.0% [7] |
| Approved for | Weight reduction and long-term maintenance (adults) | Weight reduction and maintenance; moderate to severe sleep apnea with obesity (adults) |
| Food rule | With or without food | With or without food |
| Developer | Eli Lilly | Eli Lilly |
Results come from separate trials and can't be ranked against each other. Lilly funded every trial listed. Foundayo's trials used an investigational formulation at doses that don't match the marketed tablet strengths.
The trials ran the same length and enrolled similar adults with obesity and no diabetes, which makes the gap hard to ignore. Still, they're separate studies with different placebo results, so the precise difference isn't known. A detail worth knowing: Foundayo's label says its efficacy data come from trials of an "investigational orforglipron formulation," shown as equivalent Foundayo doses [1]. The trial's 36 mg dose is not a tablet you can buy.
Using Foundayo after Zepbound
The more interesting question may be what happens when someone moves from one to the other. Stopping tirzepatide outright usually brings weight back: in SURMOUNT-4, the weight of people switched to placebo rose 14.0% over a year, while those who stayed on it lost another 5.5% [7].
ATTAIN-MAINTAIN tested a middle path. People who had lost weight on tirzepatide in an earlier trial were switched to orforglipron or placebo. At 52 weeks, the orforglipron group had kept 74.7% of their earlier loss, by the trial's model-based estimate, against 49.2% on placebo [5]. The trial had no arm that stayed on tirzepatide, and it lasted a year, so it can't say whether switching beats staying put.
Whether a switch makes sense, and at what strength, is a prescriber decision. The label doesn't give a conversion between the two drugs [1].
Daily pill vs weekly shot
Foundayo is one tablet a day, with or without food, and never more than one tablet a day, per its label [1]. That's a real difference from the Wegovy pill, which has to be taken on an empty stomach. Zepbound is one injection a week, also with or without food [2].
Both start low and build up. Foundayo's label starts at 0.8 mg a day and allows up to 17.2 mg; Zepbound's starts at 2.5 mg a week and allows up to 15 mg [1] [2]. Your prescriber sets the steps in between.
One practical note for both: both labels tell anyone relying on birth-control pills to use a backup barrier method, or a non-pill method, for some weeks once treatment begins and again whenever the dose goes up [1] [2]. Ask your prescriber how that applies to you.
Only Zepbound is approved for sleep apnea
Both labels cover adults with obesity, plus adults carrying extra weight who have a related health condition, used alongside diet and activity. Zepbound carries a second label as well, for moderate or severe obstructive sleep apnea when obesity is also present [2]. In its sleep apnea trials, tirzepatide cut breathing interruptions by about 20 to 24 events an hour more than placebo [8]. Foundayo has no sleep apnea label, and neither drug is approved for children [1].
Foundayo costs less at every price tier
| Tier | Foundayo (tablets, 30 a month) | Zepbound (vial or KwikPen) |
|---|---|---|
| Starting strength | $149 (0.8 mg) | $299 (2.5 mg) |
| Next strengths | $149 (2.5 mg) and $199 (5.5 mg), temporarily reduced through December 31, 2026 | $399 (5 mg) |
| Higher strengths | $299 (9 mg, 14.5 mg, 17.2 mg); the top two require a refill within 45 days | $449 (7.5 to 15 mg) with a refill within 45 days; otherwise $499 (7.5 mg) or $699 (10 mg and up) |
| Extra supplies | None | Needles or pen needles bought separately |
Self-pay prices from LillyDirect. Prescription required.
At the top strengths, Foundayo is $299 a month and Zepbound $449, so the pill saves $150 a month, or $1,800 a year by our arithmetic [9] [10]. If you'd rather go through a telehealth program, its fee comes on top of the medication. To compare with your own plan, try the monthly cost calculator; programs that prescribe weight pills are scored in GLP-1 pill programs.
| Program | Drug | Monthly cost | What it covers |
|---|---|---|---|
| Ro | Foundayo | $298/mo | Medication plus program fee |
| AgelessRx | Zepbound | $364/mo | Program fee plus medication from LillyDirect |
| Ro | Zepbound | $448/mo | Medication plus program fee |
Program prices from each provider's own site.
Side effects: similar kinds, different interactions
Both labels list nausea, constipation, diarrhea, vomiting and indigestion among the most common side effects, and both carry the class boxed warning about thyroid C-cell tumors in rodents [1] [2]. In the trials, more people stopped Foundayo for side effects at its higher doses than stopped Zepbound.
Foundayo has one interaction issue Zepbound doesn't: it's broken down by the liver enzyme CYP3A4. Its label limits the dose, or rules the combination out, with some medicines that strongly block or speed up that enzyme [1]. Bring a full medication list to your first visit. For the oral alternative from Novo Nordisk, see the oral semaglutide guide, and for Zepbound against Wegovy, Zepbound vs Wegovy.