What is Foundayo? A once-daily GLP-1 weight loss pill. Foundayo works by mimicking a natural gut hormone that your gut releases after eating. This hormone signals fullness and slows digestion.
Orforglipron is the active ingredient in Foundayo. The result? You eat less because you want less. Weight loss follows naturally.
In April 2026, Foundayo was US-approved for adults with obesity or overweight with a weight-related condition. These include:
- High blood pressure
- Type 2 diabetes
- Sleep apnoea
- High cholesterol
- Heart disease
In the ATTAIN-1 clinical trial, average weight loss at the highest dose of Foundayo was roughly 11% of body weight over 72 weeks. Rising to over 12.4% in patients who continued beyond the 72 weeks. They also followed a reduced-calorie diet and increased physical activity levels.
Does Foundayo have side effects?
Foundayo (orforglipron) slows stomach emptying. Appetite drops as a result, but nausea, bloating, or changes in bowel habits can also occur.
Foundayo adverse effects are mild to moderate on average. Many people find symptoms ease on their own without stopping treatment. Some barely notice side effects at all.
What are the most common Foundayo side effects?
Nausea is the side effect people report most often. It affected around one in three people in the trial. Constipation was seen by around 22–30% of the participants. Diarrhoea, 21-23%. GLP-1 medications can speed up or slow down the gut. Which one you notice depends on how your body responds.
Vomiting is more common at higher Foundayo doses, affecting up to around one in four people. Indigestion and heartburn were also common, particularly during dose escalation.
Headache, tiredness, wind, indigestion/heartburn and belching occurred less often. A smaller number noticed hair loss. Any rapid weight loss can trigger temporary thinning, and regrowth usually follows once weight stabilises.
When do Foundayo side effects start?
Foundayo (orforglipron) side effects are most common during dose escalation and tend to improve once the dose stabilises.
How long do Foundayo side effects last?
Symptoms usually improve by the time you reach a maintenance dose. For some, Foundayo side effects settle quickly. For others, they take longer to ease.
A gradual dose escalation schedule helps to reduce side effect intensity. Foundayo comes in six strengths: 0.8mg up to a maximum of 17.2mg. You start at 0.8mg, and spend at least 30 days at each step.
For some individuals, titration may take longer. Not everyone needs to reach the highest dose. A lower dose may be enough if it controls your appetite and weight is coming off.
Reach out to our clinical team if you are worried about your side effects, particularly if they are affecting your daily life, or if they are mild and haven’t eased after 2 weeks.
What can I do about side effects?
Take a low and slow approach to treatment. This is the single most effective way of managing side effects on Foundayo. Practical adjustments can also help ease symptoms:
| Symptom | What helps |
| Nausea | Smaller, more frequent meals. Bland foods such as toast or crackers before your dose. Avoid greasy or fried foods early on. Peppermint and ginger teas may help, though evidence is limited. |
| Constipation | More fibre: fruit, vegetables, wholegrain bread, and enough water. Medication if symptoms don’t improve; speak to your pharmacist. |
| Diarrhoea or vomiting | Stay hydrated. Water, clear fluids, and oral rehydration sachets or electrolytes. |
You don’t need to take Foundayo on an empty stomach or follow any food or water restrictions. Take it at whatever time of day works for you, but try to keep it consistent. Missing a dose or two is unlikely to cause problems.
Gaps of seven days or more are different. Tolerance can drop, so we may need to restart you at a lower dose and build back up. Jumping straight to a higher dose raises the risk of side effects.
Between 5% and 10% of people taking Foundayo stopped treatment because of side effects during the clinical trial. On placebo, under 3%. Most stopped during dose increases, not at maintenance. The majority continued.
Are Foundayo side effects serious?
Serious side effects are uncommon, but these side effects of Foundayo are worth knowing about:
- Severe stomach pain that won’t ease, especially if it spreads to the back. This can signal pancreatitis (inflammation of the pancreas). This is a known risk with GLP-1 medications. Stop taking Foundayo and contact a doctor straight away.
- Dehydration from vomiting and diarrhoea can trigger kidney problems. Staying hydrated helps reduce this risk.
- Foundayo has been linked to gallbladder problems. Rapid weight loss may be the cause, rather than the medication itself. Upper abdominal pain, fever, or yellowing of the skin or eyes, or clay coloured stools are key symptoms.
- Severe allergic reactions are rare. Look for swelling of the face, lips, or throat, difficulty breathing, or a rapid heartbeat. Dial 999 immediately.
- If you take diabetes medication alongside Foundayo, watch for signs of low blood sugar. These include shakiness, sweating, confusion, dizziness, or a fast heartbeat. Let your GP or diabetes clinic know before starting, as they may need to adjust your dose.
- Thyroid C-cell tumours: Foundayo carries a boxed warning. Other GLP-1 medications have caused these tumours in animal studies. Foundayo did not. No confirmed risk in humans. Notice a lump in your neck, difficulty swallowing, or hoarseness that won’t clear? Get these checked urgently.
Foundayo is not suitable for anyone with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). If you have any thyroid history, let us know before starting treatment.
Some GLP-1 medications, such as Wegovy, carry a warning about a rare eye condition called NAION (non-arteritic anterior ischaemic optic neuropathy). This has not been reported with Foundayo, but as a precaution, let us know if you notice any changes to your vision during treatment.
When should I see a doctor?
Call 999 if you have difficulty breathing, chest pain, or signs of a severe allergic reaction.
Severe stomach pain that isn’t improving, changes in eyesight or any symptom that feels like an emergency: go straight to A&E.
Not sure if it’s urgent, but something feels wrong? Call NHS 111.
Do not wait for a routine appointment.
If common side effects are bothering you, speak to our clinical team for advice.
Key takeaways
- Starting on 0.8 mg and increasing slowly gives your body time to adjust and reduces side effect intensity.
- Serious side effects are rare. Pancreatitis, kidney problems, and gallbladder problems all need urgent attention. Know the warning signs.
- Smaller meals, staying hydrated, and avoiding rich food can ease gut symptoms during the adjustment period.
- If side effects persist or get worse, we can review and adjust your treatment.
References
Orforglipron, an Oral Small-Molecule GLP-1 Receptor Agonist for Obesity Treatment (ATTAIN-1), New England Journal of Medicine, 2025 [Accessed 29 April 2026].
Foundayo (orforglipron) Prescribing Information, Eli Lilly, 2026 [Accessed 29 April 2026].
FDA Approves Lilly’s Foundayo (orforglipron), Eli Lilly, 2026 [Accessed 29 April 2026].
FDA Approves First New Molecular Entity Under National Priority Voucher Program, U.S. Food and Drug Administration, 2026 [Accessed 29 April 2026].
Authored by Shereen Amin
Pharmacist Independent Prescriber & Medical Writer
GPhC: 2073003
Shereen is a Pharmacist Independent Prescriber and medical writer with over ten years' experience across NHS primary care, digital health and specialist services. She writes evidence-based health content for Simple Online Pharmacy, turning complex clinical information into guidance patients can actually use.
Medically Reviewed by Zahra Qureshi
Senior Pharmacist
GPhC: 2216331
Zahra began her pharmacy career in community pharmacy, building a strong foundation in patient care and medication safety. She joined Simple Online Pharmacy as a locum pharmacist and quickly progressed to a senior role, supporting the pharmacy and operations teams. Zahra is passionate about ensuring patient guidance is safe, clinically sound, and easy to understand, making a positive difference to patients’ lives.
