Short answer: In the label's two placebo-controlled weight trials, the most common Foundayo side effects were nausea (26% to 35% vs 10% on placebo), constipation (20% to 27% vs 9%), diarrhea (21% to 25% vs 11%) and vomiting (13% to 24% vs 4%). Nausea, vomiting and diarrhea were higher while the dose was being raised and decreased over time. Foundayo has a boxed warning about thyroid C-cell tumors.
What Foundayo is approved for: Foundayo is approved, with a reduced-calorie diet and more physical activity, to reduce excess body weight and keep it off long term in adults with obesity, or adults with overweight and at least one weight-related condition (section 1). The label says using it with another GLP-1 receptor agonist is not recommended.
Source
FOUNDAYO (orforglipron) tablets, for oral use, prescribing information and Medication Guide. Eli Lilly. DailyMed, version published August 13, 2026. DailyMed setid 8ac446c5-feba-474f-a103-23facb9b5c62
WARNING: RISK OF THYROID C-CELL TUMORS
Medicines with GLP-1 activity in rats and mice have caused thyroid C-cell tumors in those animals. Orforglipron is not active in rats or mice and did not cause tumors in them, but it is active at the human GLP-1 receptor, and whether the rodent finding matters for people has not been determined. Foundayo must not be used by anyone with a personal or family history of medullary thyroid carcinoma (MTC) or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Symptoms of thyroid tumors include a neck mass, trouble swallowing, shortness of breath or lasting hoarseness. Routine calcitonin blood tests or thyroid ultrasound are of uncertain value for finding MTC early.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Foundayo.
| Adverse reaction | Placebo (N=1,576) % | Foundayo 5.5 mg (N=1,051) % | Foundayo 9 mg (N=1,055) % | Foundayo 17.2 mg (N=1,049) % |
|---|---|---|---|---|
| Nausea | 10 | 26 | 34 | 35 |
| Constipation | 9 | 20 | 27 | 24 |
| Diarrhea | 11 | 21 | 23 | 25 |
| Vomiting | 4 | 13 | 21 | 24 |
| Dyspepsia | 4 | 12 | 16 | 13 |
| Abdominal pain (a) | 7 | 13 | 14 | 14 |
| Headache | 7 | 8 | 9 | 9 |
| Abdominal distension | 3 | 7 | 9 | 8 |
| Fatigue (a) | 4 | 6 | 7 | 9 |
| Eructation | 1 | 6 | 8 | 8 |
| Gastroesophageal reflux disease | 2 | 6 | 6 | 7 |
| Flatulence | 2 | 5 | 6 | 6 |
| Hair loss (a) | 2 | 4 | 4 | 5 |
Two placebo-controlled trials with 3,155 adults with obesity or overweight on Foundayo once daily for up to 72 weeks; mean age 49, 41% male, 31% with type 2 diabetes. (a) Includes other related terms. Stopping because of side effects: 8% on Foundayo (6% on 5.5 mg, 9% on 9 mg, 10% on 17.2 mg) vs 3% on placebo, mostly for stomach and gut reactions.
Stomach and gut reactions overall: 60% on 5.5 mg, 68% on 9 mg and 69% on 17.2 mg vs 37% on placebo. Stopping because of them: 3%, 6% and 6% vs 0.7% on placebo. Of people on Foundayo with these reactions, 60% had mild, 36% moderate and 4% severe ones.
Heart rate: tachycardia was reported in 3% on Foundayo vs 0.9% on placebo, and the average heart rate rose 4 to 5 beats per minute from baseline vs 0.5 on placebo.
Low blood pressure: 2% on Foundayo vs 0.5% on placebo; 4% in people also on blood pressure medicine vs 1% in those not on it.
Hair loss was linked to weight reduction and was more common in women: 7% of women vs 0.9% of men on Foundayo (3% vs 0.7% on placebo).
Gallstones 1% vs 0.7% on placebo; gallbladder inflammation 0.4% vs 0.3%. Acute kidney injury 0.2% vs 0.05%. Dizziness 4% vs 3%. Taste changes 0.9% vs 0.3%. Allergic reactions 0.5% vs 0.3%. Acute pancreatitis: 6 confirmed cases on Foundayo (0.14 per 100 patient-years) vs 1 patient on placebo (0.04).
Dysesthesia (unusual skin sensations) was reported in 0.3% on 9 mg and 1% on 17.2 mg vs 0.1% on placebo; no one on 5.5 mg reported it.
In people with type 2 diabetes (Trial 2), blood sugar under 54 mg/dL was reported in 2% on Foundayo vs 0.2% on placebo; with a sulfonylurea it was 7% vs 0.5% without one. In Trial 1 (no diabetes), it was 0.6% vs none on placebo.
Pancreatic enzymes rose on average: amylase 16% to 20% and lipase 26% to 31% from baseline, vs 3% and 4% on placebo. The label says the meaning of this without other signs of pancreatitis is unknown.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Risk of thyroid C-cell tumors. The boxed warning risk. Foundayo is not for people with a personal or family history of MTC or with MEN 2. Cases of MTC have been reported after approval in people on liraglutide, another GLP-1 receptor agonist; the label says these reports cannot establish or rule out a cause.
Acute pancreatitis. Acute pancreatitis has been reported on Foundayo, and fatal and non-fatal forms have been seen with GLP-1 receptor agonists. Signs include lasting or severe stomach pain, sometimes spreading to the back. If it is suspected, Foundayo is stopped.
Severe stomach and gut reactions. Severe stomach and gut reactions were reported in about 3% on orforglipron vs 1% on placebo. Foundayo is not recommended for people with severe gastroparesis.
Kidney injury from fluid loss. Acute kidney injury, sometimes needing dialysis, has been reported, mostly after dehydration from nausea, vomiting or diarrhea. Kidney function is checked in people with these reactions, especially when starting and raising the dose.
Low blood sugar. Foundayo lowers blood sugar and can cause hypoglycemia, more so with insulin or a sulfonylurea. Lowering the dose of those medicines may reduce the risk. In people with diabetes, blood sugar is checked before and during treatment.
Serious allergic reactions. Anaphylaxis and angioedema have been reported with GLP-1 receptor agonists. If an allergic reaction happens, Foundayo is stopped. Caution applies for anyone who had these reactions with another GLP-1 receptor agonist.
Diabetic eye disease. Fast blood sugar improvement has been linked to temporary worsening of diabetic retinopathy. Foundayo has not been studied in people whose retinopathy or macular edema needs urgent treatment.
Gallbladder disease. Foundayo is linked to more acute gallbladder disease, which was associated with weight reduction. If gallbladder inflammation is suspected, the label calls for gallbladder tests.
Breathing in stomach contents during anesthesia. Foundayo slows stomach emptying. Rare cases of pulmonary aspiration under general anesthesia or deep sedation have been reported with GLP-1 receptor agonists. The label says to tell the care team about Foundayo before any planned procedure.
From the Medication Guide that comes with Foundayo:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.