Foundayo Side Effects: Common, Serious and How Long They Last

The most common side effects of Foundayo are nausea, constipation, diarrhoea, vomiting, indigestion, abdominal pain, headache, bloating, tiredness, belching, heartburn, gas and hair loss.

Most side effects are mild to moderate and affect the digestive system. They are more likely to happen when you first start treatment or after a dose increase.

Foundayo can also cause serious side effects, including pancreatitis, gallbladder problems, dehydration leading to kidney problems, low blood sugar in some people with diabetes, severe stomach problems, allergic reactions and changes in vision in people with type 2 diabetes.

You should seek urgent medical help if you develop severe, persistent abdominal pain, especially if the pain spreads to your back or happens with nausea or vomiting.

Foundayo is an oral GLP-1 tablet being developed for weight management and type 2 diabetes. It works by copying the action of GLP-1, a natural hormone involved in appetite, fullness, digestion and blood sugar regulation.

Unlike injectable GLP-1 medicines such as Wegovy and Mounjaro, Foundayo is taken as a tablet.

Further reading: How does Foundayo work?

The most common side effects of Foundayo are gastrointestinal. This means they affect the stomach and digestive system.

Commonly reported side effects include:

• nausea
• constipation
• diarrhoea
• vomiting
• indigestion
• abdominal pain
• bloating or swollen belly
• belching
• heartburn or reflux
• gas
• headache
• tiredness
• hair loss

These side effects can happen because GLP-1 medicines slow stomach emptying, reduce appetite and affect digestion. This is also part of how they help with weight loss.

For many people, digestive side effects are worse at the start of treatment and after dose increases. They may improve after the body adjusts.

Most Foundayo side effects are not serious, but some symptoms need urgent medical attention.

Pancreatitis

Pancreatitis means inflammation of the pancreas. This is a serious potential side effect of GLP-1 medicines.

Seek urgent medical help if you develop severe, persistent abdominal pain, especially if the pain spreads to your back or happens with nausea or vomiting.

If pancreatitis is suspected, treatment should usually be stopped while you are assessed. If pancreatitis is confirmed, GLP-1 treatment should not usually be restarted unless a specialist advises otherwise.

Severe stomach problems

Foundayo can cause stomach problems, and in some people these may be severe.

Speak to a clinician if you have stomach pain, nausea, vomiting, reflux, bloating or diarrhoea that is severe, persistent or getting worse.

Dehydration and kidney problems

Nausea, vomiting and diarrhoea can cause dehydration. Dehydration can put strain on the kidneys, especially in people who already have kidney problems or who take medicines that affect fluid balance.

Seek medical advice if you:

• cannot keep fluids down
• feel dizzy or faint
• pass very little urine
• feel unusually weak
• have ongoing vomiting or diarrhoea

Low blood sugar

Foundayo may increase the risk of low blood sugar if it is used with diabetes medicines that can also lower blood sugar, such as insulin or sulfonylureas.

Symptoms of low blood sugar can include:

• sweating
• shaking
• hunger
• dizziness
• headache
• blurred vision
• confusion
• fast heartbeat
• weakness
• feeling anxious or irritable

If you take diabetes medicines, your prescriber may need to adjust your treatment and advise you on blood sugar monitoring.

Gallbladder problems

GLP-1 medicines have been linked with gallbladder problems, including gallstones and inflammation of the gallbladder.

Get medical advice if you develop:

• pain in the upper abdomen
• pain after eating fatty foods
• fever
• yellowing of the skin or eyes
• pale stools
• dark urine

Serious allergic reaction

Stop treatment and seek urgent medical help if you develop symptoms of a serious allergic reaction, including:

• swelling of the face, lips, tongue or throat
• difficulty breathing or swallowing
• severe rash or itching
• feeling faint or dizzy
• very fast heartbeat

Changes in vision in people with diabetes

If you have type 2 diabetes, tell your healthcare professional if you notice changes in your vision during treatment. Changes in blood sugar control can sometimes affect diabetic eye disease.

The MHRA strengthened warnings for GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists in January 2026 because of rare reports of severe acute pancreatitis, including necrotising and fatal cases.

The MHRA advises patients to seek urgent medical attention if they develop severe, persistent abdominal pain that may spread to the back and may be accompanied by nausea or vomiting.

This warning applies to UK-authorised GLP-1 and GLP-1/GIP medicines.

Yes, nausea is one of the most common side effects of Foundayo.

It is usually more likely when starting treatment or increasing the dose of Foundayo. Nausea may improve as your body gets used to the medicine.

To help manage nausea:

• eat smaller meals
• stop eating when you feel full
• avoid greasy, fried or very rich foods
• eat slowly
• avoid large portions late at night
• sip water regularly
• avoid alcohol if it worsens nausea

Speak to a clinician if nausea is severe, does not improve or stops you eating or drinking properly.

Yes, constipation can happen with Foundayo. GLP-1 medicines can slow digestion, which may make bowel movements less frequent.

To help manage constipation:

• drink enough fluids
• increase fibre gradually
• include fruit, vegetables and whole grains
• stay physically active
• do not ignore the urge to open your bowels
• speak to a pharmacist if you need a short-term laxative

Seek medical advice if constipation is severe, painful or does not improve.

Yes, diarrhoea can happen with Foundayo. It may be more likely when starting treatment or after a dose increase.

To help manage diarrhoea:

• drink plenty of fluids
• consider oral rehydration salts if needed
• avoid greasy, spicy or rich foods
• avoid alcohol
• eat simple foods until symptoms settle

Speak to a clinician if diarrhoea is severe, persistent, bloody, or happens with dizziness, weakness or signs of dehydration.

Yes, vomiting can occur with Foundayo, especially early in treatment or after dose increases.

If you vomit:

• take small sips of water
• avoid large meals
• eat bland foods when you feel able
• avoid alcohol and fatty foods
• seek advice if vomiting continues

Get urgent medical help if you cannot keep fluids down, feel very weak, pass very little urine or have severe persistent abdominal pain.

Hair loss has been listed among reported side effects of Foundayo.

Hair shedding may also happen during significant weight loss, especially if calorie intake, protein intake or micronutrient intake drops. This type of shedding is often temporary, but it should still be assessed if it is sudden, severe or persistent.

Speak to a clinician if you notice significant hair loss while taking a weight loss medicine.

Foundayo side effects are often most noticeable when starting treatment or increasing the dose.

For many people, digestive symptoms improve over days to weeks as the body adjusts. However, some people may continue to experience symptoms for longer, especially at higher doses.

Speak to a healthcare professional if side effects:

• are severe
• do not improve
• affect eating or drinking
• cause dehydration
• interfere with daily life
• happen with warning symptoms such as severe abdominal pain

Seek urgent medical help if you develop:

• severe, persistent abdominal pain
• abdominal pain that spreads to your back
• abdominal pain with nausea or vomiting
• swelling of the face, lips, tongue or throat
• breathing difficulty
• severe rash or itching
• signs of dehydration
• vomiting that does not stop
• yellowing of the skin or eyes
• symptoms of low blood sugar if you take diabetes medicines
• sudden changes in vision if you have diabetes

For mild side effects such as nausea, constipation, reflux or headache, speak to a pharmacist or prescriber if symptoms are persistent, troublesome or do not improve.

Foundayo is an oral GLP-1 medicine with a side-effect profile that is mainly digestive. The most common side effects include nausea, constipation, diarrhoea, vomiting, indigestion, abdominal pain, headache, bloating, tiredness, belching, heartburn, gas and hair loss.

Most side effects are mild to moderate and may improve as the body adjusts. However, serious side effects can occur, including pancreatitis, gallbladder problems, dehydration, kidney problems, low blood sugar in some people with diabetes and allergic reactions.

If you develop severe persistent abdominal pain, especially if it spreads to your back or happens with nausea or vomiting, seek urgent medical help.