Foundayo side effects, in plain English

The most common Foundayo side effects

Foundayo's label pools two 72-week, placebo-controlled trials: ATTAIN-1, in adults with obesity or overweight and no diabetes, and ATTAIN-2, in adults with type 2 diabetes. In all, 3,155 adults took Foundayo.¹ The table lists the side effects reported by at least 5% of them and more often than on placebo.

Source: Foundayo prescribing information, Table 1.¹ The trials tested an investigational formulation of orforglipron, which the label reports as equivalent Foundayo doses; the journal papers use the investigational doses, 6, 12 and 36 mg.^1,3,4 The dose columns are trial groups, not a guide to your dose.

In the same two trials:

had at least one stomach side effect, depending on the dose, against 37% on placebo¹

60–69%

of people with a stomach side effect had mild ones; 36% had moderate and 4% severe ones¹

60%

stopped Foundayo because of side effects (6–10% by dose), against 3% on placebo¹

8%

stopped because of stomach side effects, against 0.7% on placebo¹

3–6%

In the separate trial papers, adverse events led 5.3–10.3% of people on orforglipron to stop in ATTAIN-1 (2.7% on placebo), and 6.1–9.9% in ATTAIN-2, in people with type 2 diabetes (4.1% on placebo).^3,4

When Foundayo side effects happen, and when they ease

The label gives no week-by-week timeline, and nobody can predict yours. It does describe a pattern.

1. Starting out
   A low start

   Foundayo comes in six strengths, from 0.8 mg to 17.2 mg. Labels start low and step up gradually; your prescriber sets the steps.¹

2. During each step up
   When they were most common

   Nausea, vomiting and diarrhea were more common during the dose-escalation period.¹ The weeks after a change are the ones most worth writing down.

3. The months that follow
   Usually easing

   Those effects then decreased over time.¹

4. If it doesn't settle
   Tell your care team

   The Medication Guide asks you to tell your healthcare provider about stomach problems that are severe or won't go away, and to tell them right away about nausea, vomiting or diarrhea that doesn't go away.¹

What's different about a daily pill

Foundayo, approved by the FDA in April 2026 for weight management, is a once-daily tablet you can take at any time of day, with or without food.^1,2,7 Its label sets no fasting, water or waiting rules:¹ orforglipron is a small-molecule GLP-1 medicine rather than a peptide,³ and the FDA describes it as a pill that doesn't need to be taken on an empty stomach.² How that compares with the Wegovy pill is covered in Foundayo vs Wegovy.

The label's practical rules are short: it says to swallow the tablet whole, without breaking, crushing or chewing it, and not to take more than one tablet a day.¹ For missed doses, Foundayo's Medication Guide has its own rule, including for a longer gap, so ask your prescriber or pharmacist rather than guessing. Handle records what happened and never tells you to catch up.

Two more label points are easy to miss. Orforglipron is broken down mainly by the enzyme CYP3A4, and the label lists interactions with some medicines, including clarithromycin, carbamazepine, ritonavir and simvastatin, so tell your prescriber and pharmacist about everything you take.¹ And Foundayo may make birth control pills taken by mouth work less well: 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.¹

One by one: what may help and when to call

General, non-drug measures only, from the Medication Guide; your care team can advise on anything more.

• Nausea (26–35% vs 10% on placebo).¹ Drinking fluids matters: the Medication Guide says it helps reduce your chance of dehydration.¹ Ask your care team whether changing what or how much you eat might help, and call them if nausea stops you eating or drinking, or doesn't go away.
• Constipation (20–27% vs 9%).¹ One of the most common effects on Foundayo. Ask your care team whether more fiber and fluids would suit you, and call them if it's severe or won't go away.
• Diarrhea (21–25% vs 11%).¹ Keep drinking: the Medication Guide says fluids help lower your chance of dehydration, which can lead to kidney problems. Tell your care team right away if it doesn't go away.¹
• Vomiting (13–24% vs 4%).¹ Vomiting can lead to dehydration, so ask your care team how best to keep fluids up.¹ Tell your care team right away if vomiting doesn't stop or you can't keep fluids down.
• Indigestion, heartburn and burping. Indigestion (12–16% vs 4%), reflux (6–7% vs 2%) and burping (6–8% vs 1%) were all more common than on placebo.¹ Ask your care team whether changes to your meals might help. The label says nothing about smell: "sulfur burps" is not a label term.
• Stomach pain, bloating and gas. Stomach pain (13–14% vs 7%), bloating (7–9% vs 3%) and gas (5–6% vs 2%).¹ Severe stomach pain that won't go away is different: see the red flags below.
• Headache (8–9% vs 7%).¹ Only a little more common than on placebo. If you also use insulin or a sulfonylurea, headache can be a sign of low blood sugar.¹
• Tiredness (6–9% vs 4%).¹ Worth mentioning to your care team if it's new or doesn't lift.

Less talked-about Foundayo side effects

Beyond the stomach, this is what the label says about the effects people often ask about.

• Hair loss. Reported by 4–5% of people on Foundayo against 2% on placebo, and more often by women (7%) than men (0.9%); on placebo the figures were 3% and 0.7%.¹
• Dizziness and low blood pressure. Dizziness affected 4% against 3%. Low blood pressure affected 2% against 0.5%, and 4% of people on Foundayo who also took blood-pressure medicines.¹
• A faster heartbeat. A fast heart rate (tachycardia) was reported by 3% against 0.9%, and average heart rate rose by 4–5 beats per minute, against 0.5 on placebo.¹
• Taste and skin changes. Changes in taste affected 0.9% against 0.3%, and altered skin sensation (dysesthesia) 0.3% at 9 mg and 1% at 17.2 mg, against 0.1% on placebo.¹
• Liver. Liver problems are not among the label's warnings, but the label says Foundayo is not recommended for people with severe liver impairment.¹
• Mood. Foundayo's label has no warning about suicidal thoughts.¹ In January 2026 the FDA asked for that warning to be removed from the GLP-1 labels that carried it, after a review found no increased risk, and it still asks you to report new or worsening depression or unusual changes in mood.⁵
• Muscle and lean mass. The label says orforglipron lowers body weight with greater fat mass loss than lean mass loss.¹ Lean mass is not the same thing as muscle.

Serious side effects of Foundayo (orforglipron)

Serious side effects are less common, and each has signs worth knowing. These are the label's main warnings.

• Pancreatitis. Confirmed in 6 people on Foundayo (0.14 people per 100 years of use) against 1 on placebo (0.04).¹ The warning sign is severe stomach pain that won't go away; see the red flags below.
• Gallbladder problems. Gallstones in 1% against 0.7%, and acute gallbladder inflammation in 0.4% against 0.3%.¹
• Kidney problems from dehydration. Acute kidney injury in 0.2% against 0.05%.¹ Nausea, vomiting and diarrhea can cause the fluid loss behind it.¹
• Severe stomach problems. About 3% against 1%, and Foundayo is not recommended for people with severe gastroparesis.¹
• Low blood sugar. Mainly with insulin or a sulfonylurea: in ATTAIN-2, 2% of people with type 2 diabetes had a reading below 54 mg/dL against 0.2% on placebo, and 7% of those also taking a sulfonylurea did.¹
• Allergic reactions. Reported in 0.5% against 0.3%.¹
• Eye changes in type 2 diabetes. The label warns about diabetic retinopathy complications in people with type 2 diabetes; report any change in your vision.¹
• Food in the lungs under anesthesia. Rare reports in people taking GLP-1 medicines. Tell every healthcare provider you take Foundayo before surgery or sedation.¹

Who should not take Foundayo

Foundayo carries a boxed warning about thyroid C-cell tumors.¹ Its wording is unusual: orforglipron is not active in rats or mice and did not cause tumors in rodents, and while it does act on the human GLP-1 receptor, the label says the human relevance of the thyroid tumors seen in rodents with this type of medicine has not been determined.¹

The label says not to take Foundayo if you or a family member has had medullary thyroid carcinoma (MTC), if you have multiple endocrine neoplasia syndrome type 2 (MEN 2), or if you've had a serious allergic reaction to orforglipron or its ingredients. Tell your provider about a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath.¹

It isn't recommended with other GLP-1 medicines, or for people with severe gastroparesis or severe liver impairment, and its safety and effectiveness in children have not been established.¹ The label also warns of possible harm to an unborn baby and says Foundayo isn't recommended while breastfeeding, so tell your prescriber if you're pregnant, planning a pregnancy or breastfeeding.¹

How Foundayo compares with other GLP-1 medicines

The labels themselves say side-effect rates from different medicines' trials can't be compared directly,¹ and Foundayo has not been tested head-to-head against the Wegovy pill for weight loss.

One head-to-head trial is in type 2 diabetes. ACHIEVE-3 compared orforglipron with oral semaglutide at Rybelsus doses, not the Wegovy pill, in 1,698 adults over 52 weeks, open-label: 8.7% and 9.7% stopped orforglipron because of adverse events, against 4.5% and 4.9% on oral semaglutide.⁶

For the wider picture, see Foundayo vs Zepbound, our pages on Zepbound side effects and Wegovy side effects, or the full list of GLP-1 medications.

Foundayo side effects in the UK

The MHRA authorised Foundayo on 10 August 2026, making the UK the first country in Europe to approve it, for weight management and, unlike in the US, for type 2 diabetes too.⁷ It is not currently available on the NHS while NICE evaluates it, and you can report suspected side effects to the MHRA's Yellow Card scheme.⁷

Tracking Foundayo in Handle

Foundayo isn't in Handle's medicine list yet. Add it under "Something else" with its name, the amount your prescriber set and a daily schedule; logging doses, the check-in, weight, food, Journey and the Premium report then work the same way. Our Foundayo tracker guide walks through it, and the GLP-1 side effect tracker checklist covers what to note.

Questions to ask your prescriber

1. Which side effects should I call you about, and which can I manage at home?
2. What should I do if I can't keep fluids down?
3. Do any of my other medicines interact with Foundayo?
4. I use the contraceptive pill. What should I use alongside it, and for how long?
5. What should I do if I miss a dose, or several days? Foundayo's instructions have their own rule.

For side effects across the whole class of medicines, see our overview of GLP-1 side effects.