In short
- Foundayo is orforglipron, a once-daily GLP-1 pill; Zepbound is tirzepatide, a once-weekly GIP and GLP-1 injection. Both are made by Eli Lilly and FDA-approved for weight reduction in adults.
- In separate 72-week trials of adults without diabetes, Foundayo 17.2 mg averaged 11.1% weight loss (2.1% on placebo) and Zepbound 15 mg averaged 20.9% (3.1% on placebo). No trial has compared them head to head.
- In ATTAIN-MAINTAIN, people who switched from tirzepatide to orforglipron kept an estimated 74.7% of their weight loss after 52 weeks, against 49.2% for those switched to placebo.
- As of October 27, 2026, LillyDirect charges $149 to $299 a month for Foundayo and $299 to $449 for Zepbound, with Zepbound’s $449 at 7.5 mg and up only when you refill within 45 days.
- Both carry a boxed warning for thyroid C-cell tumors. Nausea affected 26% to 35% of people on Foundayo and 25% to 29% on Zepbound in their main trials.
Zepbound produced about twice the average weight loss of Foundayo in their main trials, 20.9% against 11.1% over 72 weeks at the top doses, but Foundayo is a daily pill you can take any time, with or without food, and it costs less. Both are Eli Lilly drugs approved for weight reduction in adults: Foundayo is orforglipron, a GLP-1 pill, and Zepbound is tirzepatide, a weekly injection that acts on GIP and GLP-1.
No trial has tested them against each other for weight loss. Below are the results each drug posted, what happened when people switched from one to the other, and what each costs as of October 27, 2026.
Foundayo and Zepbound at a glance
| Foundayo | Zepbound | |
|---|---|---|
| Active ingredient | Orforglipron (GLP-1), a small molecule | Tirzepatide (GIP and GLP-1), a peptide |
| Form | Tablet, once daily | Injection, once weekly |
| FDA-approved for | Weight reduction (adults) | Weight reduction (adults); obstructive sleep apnea with obesity |
| Approved | April 1, 2026 | November 8, 2023 |
| Food rules | None: any time of day, with or without food | None: any time of day, with or without meals |
| Doses | 0.8, 2.5, 5.5, 9, 14.5, 17.2 mg | 2.5, 5, 7.5, 10, 12.5, 15 mg |
| Main trial, top dose | 11.1% at 72 weeks (ATTAIN-1) | 20.9% at 72 weeks (SURMOUNT-1) |
| Boxed warning | Thyroid C-cell tumors | Thyroid C-cell tumors |
| Self-pay (Oct 27, 2026) | $149 to $299 a month | $299 to $449 a month, with refills within 45 days |
| Medicare GLP-1 Bridge | Listed | KwikPen listed |
Sources: the Foundayo and Zepbound labels, Lilly, LillyDirect and the CMS Bridge form.
Weight loss: ATTAIN vs SURMOUNT
Each drug was tested against placebo in adults with obesity, or overweight with a weight-related condition, alongside diet and activity advice. These figures count everyone assigned to each group, as FDA labels do.
Scroll sideways to see the full table
| Trial | Who | Drug and doses | Length | Average weight change | Placebo |
|---|---|---|---|---|---|
| ATTAIN-1 | 3,127 adults without diabetes | Foundayo 5.5 / 9 / 17.2 mg | 72 weeks | -7.4% / -8.3% / -11.1% | -2.1% |
| SURMOUNT-1 | 2,539 adults without diabetes | Zepbound 5 / 10 / 15 mg | 72 weeks | -15.0% / -19.5% / -20.9% | -3.1% |
| ATTAIN-2 | 1,613 adults with type 2 diabetes | Foundayo 5.5 / 9 / 17.2 mg | 72 weeks | -5.1% / -7.0% / -9.6% | -2.5% |
| SURMOUNT-2 | 938 adults with type 2 diabetes | Zepbound 10 / 15 mg | 72 weeks | -12.8% / -14.7% | -3.2% |
Sources: Foundayo label, Table 6; Zepbound label, Table 2.
The share of people who lost at least 20% of their weight shows the gap plainly: 18.4% on Foundayo 17.2 mg in ATTAIN-1, against 56.7% on Zepbound 15 mg in SURMOUNT-1. Both trials ran 72 weeks in similar volunteers, but they were separate trials, so this is an indirect comparison.
One detail can confuse readers. ATTAIN-1 in the New England Journal of Medicine reports doses of 6, 12 and 36 mg. The trials used an investigational formulation, and the Foundayo label shows those results at the equivalent marketed doses of 5.5, 9 and 17.2 mg.
Orforglipron vs tirzepatide after a switch
The closest thing to a head-to-head is ATTAIN-MAINTAIN, a 52-week, double-blind Lilly trial published in Nature Medicine in 2026. It took people who had lost weight on tirzepatide (205 adults) or semaglutide (171 adults) in SURMOUNT-5 and switched them to daily orforglipron or to placebo.
Among those coming off tirzepatide who had reached a weight plateau, the orforglipron group kept an estimated 74.7% of the weight they had lost, against 49.2% in the placebo group. Those coming off semaglutide kept 79.3% against 37.6%. The figures are model-based estimates.
Two limits matter. No group stayed on tirzepatide, so the trial can’t say whether switching keeps as much off as continuing the injection. And it ran one year. Still, it’s the main evidence for people weighing a move from Zepbound to a pill, and the decision belongs with your prescriber.
Side effects
Both labels carry a boxed warning for thyroid C-cell tumors, and neither drug is for anyone with a personal or family history of medullary thyroid carcinoma or MEN 2. Tirzepatide caused these tumors in rats. Orforglipron isn’t active in rats or mice and caused no tumors in them, but it does act on the human GLP-1 receptor, and Foundayo’s label carries the same warning.
Stomach side effects lead on both, mostly while the dose is rising. Rates come from each label’s pooled weight trials; compare each drug with its own placebo.
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| Side effect | Foundayo 5.5 / 9 / 17.2 mg | Its placebo | Zepbound 5 / 10 / 15 mg | Its placebo |
|---|---|---|---|---|
| Nausea | 26% / 34% / 35% | 10% | 25% / 29% / 28% | 8% |
| Constipation | 20% / 27% / 24% | 9% | 17% / 14% / 11% | 5% |
| Diarrhea | 21% / 23% / 25% | 11% | 19% / 21% / 23% | 8% |
| Vomiting | 13% / 21% / 24% | 4% | 8% / 11% / 13% | 2% |
| Stopped because of side effects | 6% / 9% / 10% | 3% | 4.8% / 6.3% / 6.7% | 3.4% |
In these separate trials, vomiting was more common on Foundayo, and a larger share of people stopped it because of side effects. Both labels also warn about pancreatitis, gallbladder disease, low blood sugar, kidney injury from dehydration and severe stomach problems. See our Zepbound side effects and GLP-1 side effects guides.
How you take each one
Foundayo is one tablet a day, at any time of day, with or without food; Lilly says it has no food or water restrictions. Swallow it whole; don’t split, crush or chew it. It starts at 0.8 mg, rises to 2.5 mg and then 5.5 mg, each after at least 30 days, and can go to 9, 14.5 or 17.2 mg, one step at a time and at least 30 days apart, depending on response and tolerance. The label caps the dose at 9 mg if you take a strong CYP3A4 inhibitor, a type of drug interaction your prescriber checks for, and limits simvastatin to 20 mg a day.
Zepbound is one injection a week, at any time of day, with or without meals. It starts at 2.5 mg for 4 weeks and rises in 2.5 mg steps at least 4 weeks apart, to a maintenance dose of 5, 10 or 15 mg. It comes as single-dose vials you draw into a syringe, single-dose pens and a KwikPen that holds four doses.
Both can make birth control pills less reliable. If you use oral contraceptives, both labels advise switching to a non-oral method or adding a barrier method after starting and after each dose increase: for 30 days on Foundayo and 4 weeks on Zepbound.
What each costs in October 2026
These are LillyDirect’s self-pay prices, read on October 27, 2026. A Foundayo month is 30 days; a Zepbound month is 4 weekly doses (28 days).
| Fill | Foundayo | Zepbound (vial or KwikPen) |
|---|---|---|
| 1 | 0.8 mg: $149 | 2.5 mg: $299 |
| 2 | 2.5 mg: $149 (reduced through Dec 31, 2026) | 5 mg: $399 |
| 3 | 5.5 mg: $199 (reduced through Dec 31, 2026) | 7.5 mg: $449 with a refill within 45 days |
| Ongoing | 9 to 17.2 mg: $299 (with a refill within 45 days at 14.5 and 17.2 mg) | 10 to 15 mg: $449 with a refill within 45 days |
| Late refill | $349 at 14.5 or 17.2 mg | $499 at 7.5 mg; $699 at 10 to 15 mg |
| First 12 fills | $3,188 | $5,188 |
Sources: LillyDirect Foundayo, Foundayo offer terms and LillyDirect Zepbound. At maintenance, Foundayo costs $150 a month less than Zepbound with on-time refills. If your Zepbound dose stays at 5 mg, 12 fills come to $4,688. Lilly’s temporary Foundayo cuts end December 31, 2026, when its regular prices of $199 at 2.5 mg and $299 at 5.5 mg return. Our Foundayo cost and Zepbound cost guides go dose by dose.
Foundayo vs Wegovy
Foundayo is also often compared with Novo Nordisk’s Wegovy. On the Wegovy label, the weekly injection averaged 14.9% weight loss at 2.4 mg over 68 weeks (2.4% on placebo), and the daily Wegovy pill 13.6% at 25 mg over 64 weeks (2.4% on placebo). The Wegovy pill must be taken in the morning on an empty stomach with up to 4 ounces of water, unlike Foundayo.
As of October 27, 2026, NovoCare sells the Wegovy pill at $149 to $299 a month and the injection at $199 for each of the first two fills for new patients, then $349. Our Foundayo vs Wegovy pill guide compares the two pills in full.
Medicare and insurance
Both drugs are on the Medicare GLP-1 Bridge, where eligible Part D enrollees pay $50 a month from July 1, 2026 to December 31, 2027. The CMS form lists Foundayo and the Zepbound KwikPen for weight-loss prescriptions; sleep apnea prescriptions for Zepbound go to your regular Part D plan. See does Medicare cover Wegovy or Zepbound.
With commercial insurance that covers the drug, Lilly’s savings cards can bring Foundayo or the Zepbound single-dose pen to as little as $25 a month. People with Medicare, Medicaid or other government coverage can’t use them. Our insurance guide covers how plans treat weight-loss drugs.
Which one fits you
- For the largest average weight loss, Zepbound led by a wide margin in its trials.
- If you’d rather not inject, Foundayo is a pill, and unlike the Wegovy pill it has no food or water rules.
- On cost, Foundayo is $150 a month less at maintenance and $2,000 less over the first 12 fills.
- With obstructive sleep apnea and obesity, Zepbound is the one approved for it.
- If you take a strong CYP3A4 inhibitor, Foundayo’s top dose is limited to 9 mg.
- If you’ve reached your goal on Zepbound, ATTAIN-MAINTAIN is evidence that a switch to Foundayo can hold much of the loss; ask your prescriber.
A licensed clinician can weigh these with your history, other medicines and coverage. Compare programs on our GLP-1 pill rankings and Zepbound rankings, or use our match tool.
The bottom line
Foundayo and Zepbound are both Lilly drugs approved for weight reduction. Zepbound, a weekly injection, averaged 20.9% weight loss at 15 mg over 72 weeks; Foundayo, a daily pill with no food rules, averaged 11.1% at 17.2 mg over the same length of time, in a separate trial. As of October 27, 2026, Foundayo costs $149 to $299 a month at LillyDirect against $299 to $449 for Zepbound with refills within 45 days. Choose with a licensed clinician, and see our weight-loss hub for more options.
Where to get Zepbound or Foundayo online
The three highest-scored programs that publish a price for Zepbound or Foundayo, with that price.
- Safety: GLP-1 medications carry a boxed warning for thyroid C-cell tumors. Read the safety information
- 01
Rated 9.1 out of 10, Excellent
From $1,498/mo $1,399 + $99/mo membership
Visit site for Eden (opens in a new tab) - 02Measured
Low compounded prices, plus prior authorization help for brand-name GLP-1s
Rated 9.0 out of 10, Excellent
From $398/mo $299 + $99/mo membership
Visit site for Measured (opens in a new tab) - 03Found
Using insurance for visits, with compounded medication in one plan
Rated 8.5 out of 10, Very good
From $811/mo $650 + $161.42/mo membership
Visit site for Found (opens in a new tab)
Questions, answered
Is Foundayo as effective as Zepbound?
Foundayo vs tirzepatide: can I switch from Zepbound to Foundayo?
Is orforglipron stronger than tirzepatide?
Foundayo vs Wegovy: how do they compare?
Which costs less, Foundayo or Zepbound?
Sources
- Eli Lilly: Foundayo prescribing information (rev. 07/2026)
- Eli Lilly: Zepbound prescribing information (rev. 08/2026)
- Wharton et al., Orforglipron, an Oral Small-Molecule GLP-1 Receptor Agonist for Obesity Treatment (ATTAIN-1), N Engl J Med 2025
- Aronne et al., Orforglipron for maintenance of body weight reduction (ATTAIN-MAINTAIN), Nat Med 2026
- Eli Lilly via PR Newswire: Foundayo now available in the US (Apr 9, 2026)
- DailyMed: Wegovy injection and tablets prescribing information (rev. 06/2026)
- Eli Lilly: LillyDirect Foundayo self-pay prices (read Oct 27, 2026)
- Eli Lilly: Foundayo coverage, savings and offer terms (read Oct 27, 2026)
- Eli Lilly: LillyDirect Zepbound self-pay prices (read Oct 27, 2026)
- NovoCare: Wegovy self-pay prices (read Oct 27, 2026)
- CMS: Medicare GLP-1 Bridge (read Oct 27, 2026)
- CMS: Medicare GLP-1 Bridge prior authorization form (read Oct 27, 2026)