Independent UK medicine guidance
Can Mounjaro affect your kidneys?
Mounjaro is not generally described as directly toxic to the kidneys. The main recognised risk is indirect: nausea, vomiting and diarrhoea can cause dehydration, which may reduce kidney function and, in serious cases, contribute to acute kidney injury. Older adults and people with existing kidney problems may be more vulnerable.
Signs of dehydration
- Dark, strong-smelling urine
- Urinating less frequently
- Dry mouth, lips or tongue
- Thirst
- Headache
- Dizziness or light-headedness
- Unusual tiredness
- Sunken eyes
More concerning symptoms include passing very little urine, confusion, severe weakness, breathlessness or swelling in the feet and legs.
How can you protect yourself?
Drink regularly throughout the day. If nausea makes drinking difficult, try small, frequent sips rather than a large glass at once.
Vomiting and diarrhoea cause the loss of water and salts. A pharmacist may recommend a suitable oral rehydration solution.
Other medicines matter
Dehydration can alter the safety of medicines including certain blood-pressure treatments, diuretics, anti-inflammatory painkillers, metformin and SGLT2 inhibitors.
“Sick day” advice varies according to your conditions and medication. Do not stop several prescribed medicines based on a generic list without speaking to a pharmacist, GP, diabetes team or NHS 111.
Never stop insulin because you are unwell unless a specialist explicitly tells you to do so.
Read the full guide to sick-day rules
When should you seek help?
Contact your prescriber, GP or NHS 111 if:
- You cannot keep fluids down
- Vomiting or diarrhoea is persistent
- You are passing much less urine
- You become faint, confused or extremely drowsy
- You have existing kidney disease and develop dehydration
- You take medicines that may need adjustment during illness
Blood tests may be needed to check kidney function and electrolyte levels.
Common questions
Is Mounjaro bad for your kidneys?
Mounjaro is not generally described as directly toxic to the kidneys. The main recognised risk is indirect: nausea, vomiting and diarrhoea can cause dehydration, which may reduce kidney function and, in serious cases, contribute to acute kidney injury. Older adults and people with existing kidney problems may be more vulnerable.
What are the signs of dehydration to watch for?
Dark, strong-smelling urine, urinating less frequently, dry mouth, lips or tongue, thirst, headache, dizziness or light-headedness, unusual tiredness and sunken eyes. More concerning symptoms include passing very little urine, confusion, severe weakness, breathlessness or swelling in the feet and legs.
Should I stop other medicines if I get dehydrated?
Do not stop several prescribed medicines based on a generic list. Dehydration can alter the safety of certain blood-pressure treatments, diuretics, anti-inflammatory painkillers, metformin and SGLT2 inhibitors, but sick-day advice varies by condition and medication, so speak to a pharmacist, GP, diabetes team or NHS 111. Never stop insulin unless a specialist explicitly tells you to.
Related guides
Sources: Mounjaro Summary of Product Characteristics (eMC) • NHS dehydration guidance • NHS acute kidney injury guidance
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