Foundayo Side Effects: What to Expect
Every reaction the orforglipron trial program recorded, alongside the boxed warning and the Section 5 risks its FDA label carries.
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Most Common Foundayo Side Effects
Every reaction the Foundayo FDA label records, showing how often it appeared among orforglipron-treated patients and how often it appeared on placebo. The figures are taken from the label's Section 6, DailyMed SetID8ac446c5-feba-474f-a103-23facb9b5c62.
| Adverse reaction | Incidence (Foundayo vs placebo) |
|---|---|
| Nausea | 26–35% (placebo 10%) |
| Constipation | 20–27% (placebo 9%) |
| Diarrhea | 21–25% (placebo 11%) |
| Vomiting | 13–24% (placebo 4%) |
| Dyspepsia | 12–16% (placebo 4%) |
| Abdominal pain | 13–14% (placebo 7%) |
| Headache | 8–9% (placebo 7%) |
| Abdominal distension | 7–9% (placebo 3%) |
| Fatigue | 6–9% (placebo 4%) |
| Eructation | 6–8% (placebo 1%) |
| Gastroesophageal reflux disease | 6–7% (placebo 2%) |
| Flatulence | 5–6% (placebo 2%) |
| Hair loss | 4–5% (placebo 2%) |
Source: Foundayo FDA prescribing information via DailyMed (SetID 8ac446c5-feba-474f-a103-23facb9b5c62), Section 6 Adverse Reactions, read on 2026-09-27. Treat this as a summary — the full label is the document, and a prescriber is the person to discuss it with.
Boxed Warning — Thyroid C-Cell Tumors
“In products with glucagon-like peptide-1 (GLP-1) receptor agonist activity that are pharmacologically active in rats and mice, rodent thyroid C-cell tumors (adenomas and carcinomas) have been observed at clinically relevant exposures and are considered GLP-1 receptor-dependent effects in rodents. Orforglipron is not pharmacologically active in rats or mice and did not produce tumors in rodents. While orforglipron is pharmacologically active at the human GLP-1 receptor, the human relevance of GLP-1 receptor-dependent thyroid C-cell tumors observed in rodents has not been determined. FOUNDAYO is contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).”
Quoted word for word from the Foundayo FDA label (DailyMed SetID 8ac446c5-feba-474f-a103-23facb9b5c62). Nothing the FDA issues carries more weight than a boxed warning. Your own history and your family's both need to be on the table before you start Foundayo, and that means talking to a licensed prescriber.
Serious Warnings & Precautions
Past the everyday reactions above, Section 5 of the Foundayo label sets out these serious risks. They arrive far less often, and some of them need care the same day — which is why the symptoms are worth knowing and when to seek care.
- Risk of thyroid C-cell tumors
- Acute pancreatitis
- Severe gastrointestinal reactions
- Acute kidney injury due to volume depletion
- Hypoglycemia
- Hypersensitivity reactions
- Diabetic retinopathy complications in patients with type 2 diabetes
- Acute gallbladder disease
- Pulmonary aspiration during general anesthesia or deep sedation
Compare every Foundayo provider
Every warning above is something a prescriber screens for before writing anything. Current price, verification status, product form and the states each seller ships to are all on one screen.
Related deep-dives
What to do about each symptom, and the evidence underneath it, is covered here: