Foundayo side effects
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Most common side effects, by dose
The FDA label lists side effects reported in at least 5% of people on Foundayo and more often than on placebo, from two placebo-controlled weight-management trials lasting up to 72 weeks.
| Side effect | Placebo | 5.5 mg | 9 mg | 17.2 mg |
|---|---|---|---|---|
| Nausea | 10% | 26% | 34% | 35% |
| Constipation | 9% | 20% | 27% | 24% |
| Diarrhea | 11% | 21% | 23% | 25% |
| Vomiting | 4% | 13% | 21% | 24% |
| Indigestion (dyspepsia) | 4% | 12% | 16% | 13% |
| Stomach pain | 7% | 13% | 14% | 14% |
| Headache | 7% | 8% | 9% | 9% |
| Bloating (abdominal distension) | 3% | 7% | 9% | 8% |
| Fatigue | 4% | 6% | 7% | 9% |
| Belching | 1% | 6% | 8% | 8% |
| Acid reflux (GERD) | 2% | 6% | 6% | 7% |
| Gas | 2% | 5% | 6% | 6% |
| Hair loss | 2% | 4% | 4% | 5% |
Source: Foundayo prescribing information (revised 07/2026), Table 1. The label reports only the 5.5, 9 and 17.2 mg doses. Stomach pain, fatigue and hair loss include related terms. Hair loss was more common in women (7%) than men (0.9%) on Foundayo.
How often stomach side effects happen, and when
- Any digestive side effect: 60% (5.5 mg), 68% (9 mg) and 69% (17.2 mg), versus 37% on placebo.
- Of people on Foundayo who had them, 60% rated them mild, 36% moderate and 4% severe.
- Nausea, vomiting and diarrhea were more frequent while the dose was being stepped up, then decreased over time.
That's why the label has you start low: 0.8 mg once daily, then 2.5 mg and 5.5 mg, with at least 30 days at each step. Your clinician may then go to 9, 14.5 or 17.2 mg based on how you respond and tolerate it. If you miss 7 or more doses in a row, call your clinician; the label says to restart at a lower dose.
How many people stopped because of side effects
Across both trials, 8% of people on Foundayo stopped for good because of side effects (6% on 5.5 mg, 9% on 9 mg, 10% on 17.2 mg), versus 3% on placebo. Most of those stopped because of digestive side effects.
Boxed warning: thyroid C-cell tumors
Like other GLP-1 medicines, Foundayo carries a boxed warning about thyroid C-cell tumors. The label notes that orforglipron isn't active in rats or mice and didn't cause tumors in rodents, and that it isn't known whether it causes thyroid tumors in people. Don't take Foundayo if you or a family member has had medullary thyroid carcinoma (MTC) or you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Tell your clinician about a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath.
Serious side effects to know
- Pancreatitis: severe stomach pain that won't go away, with or without vomiting, sometimes felt through to the back. Stop Foundayo and call your clinician right away.
- Severe stomach problems: reported in about 3% of people on orforglipron versus 1% on placebo. Foundayo isn't recommended for people with severe gastroparesis.
- Kidney injury from dehydration: mostly in people who had vomiting or diarrhea. Drink fluids, and call your clinician if nausea, vomiting or diarrhea won't go away.
- Gallbladder problems: watch for upper-stomach pain, fever, yellow skin or eyes, or clay-colored stools.
- Low blood sugar, mainly if you also take insulin or a sulfonylurea; your clinician may lower those doses.
- Serious allergic reactions: swelling of the face, lips, tongue or throat, trouble breathing or swallowing, severe rash, fainting, or a very fast heartbeat. Get medical help right away.
- Vision changes in people with type 2 diabetes: tell your clinician.
- Aspiration during anesthesia or deep sedation: tell every clinician before surgery or a procedure that you take Foundayo.
The label also reports a faster heart rate (3% vs 0.9% on placebo, an average increase of 4 to 5 beats per minute), low blood pressure (2% vs 0.5%) and dizziness (4% vs 3%).
Medicines and birth control
- Birth control pills: Foundayo slows stomach emptying, which may affect how oral medicines are absorbed. The label advises switching to a non-oral method, or adding a barrier method, for 30 days after starting and for 30 days after each dose increase.
- Other drugs: strong CYP3A4 inhibitors cap Foundayo at 9 mg, and some should be avoided altogether, as should strong CYP3A4 inducers. Simvastatin shouldn't go above 20 mg a day. Ask your pharmacist to check your list.
- Pregnancy and breastfeeding: Foundayo may harm an unborn baby; stop it when pregnancy is recognized. It isn't recommended while breastfeeding.
- Don't take Foundayo with another GLP-1 medicine.
Taking it correctly
Take one tablet once a day, with or without food. Swallow it whole; don't break, crush or chew it, and don't take more than one tablet a day.
To report a side effect, contact Lilly at 1-800-545-5979 or the FDA at 1-800-FDA-1088 or fda.gov/medwatch.
Questions about side effects?
A clinician can review your history, your other medicines and your dose plan. See where to get a prescription.
FAQ
What are the most common Foundayo side effects?
Nausea, constipation, diarrhea, vomiting, indigestion, stomach pain, headache, bloating, fatigue, belching, acid reflux, gas and hair loss, each listed in the label as reported in at least 5% of people on Foundayo (hair loss was 4% to 5% depending on dose). Nausea affected 26% to 35% depending on dose, versus 10% on placebo.
Do Foundayo side effects go away?
For many people they ease. The label says nausea, vomiting and diarrhea were more frequent while the dose was being increased and decreased over time, and most digestive side effects were mild or moderate.
How many people stop Foundayo because of side effects?
In the label's trials, 8% of people on Foundayo stopped because of side effects (6% to 10% depending on dose), compared with 3% on placebo.
Does Foundayo have a boxed warning?
Yes. Like other GLP-1 medicines, it has a boxed warning about thyroid C-cell tumors and isn't for people with a personal or family history of medullary thyroid carcinoma or with MEN 2.
Can I take Foundayo with birth control pills?
The label advises switching to a non-oral method or adding a barrier method for 30 days after starting Foundayo and for 30 days after each dose increase, because it may affect how oral medicines are absorbed.