Medicine sick day rules
Taking certain medication when you are dehydrated or very unwell can lead to more serious illness. This is because they can increase the risk of serious side effects affecting your kidneys when you are dehydrated. This can be caused by:
- Diarrhoea or vomiting (unless very minor)
- Fever (high temperature), sweats or shaking
- Not drinking enough (insufficient fluid intake)
These medications should be temporarily stopped if you are at risk of becoming dehydrated. This are known as sick day rules.
They can be restarted when you are well again, usually after 24-48 hours of eating and drinking normally.
Which illnesses cause dehydration?
Vomiting, diarrhoea, fever (high temperature), sweats, shaking and insufficient fluid intake can all lead to dehydration.
Which medication should I stop?
- ACE inhibitors & ARBs: names ending in “pril” or “sartan” – e.g. Lisinopril, Ramipril, Candesartan, Losartan. A medication for high blood pressure and heart conditions.
- Entresto (Sacubitril/Valsartan): contains a combination of both an ACE inhibitor and an ARB. A medication for heart conditions.
- Diuretics: water tablets – e.g. Furosemide, Spironolactone, Eplerenone, Bendroflumethiazide. A medication for excess fluid, high blood pressure and heart conditions.
- SGLT2 inhibitors: names ending in “flozin” – e.g. Dapagliflozin, Empagliflozin, Canagliflozin. A medication for diabetes, kidney or heart conditions.
- Diabetes & Weight Loss Medications:
- Metformin: A medication for diabetes.
- Sulfonylureas: e.g. Gliclazide, Glimepiride, Glipizide. A medication for diabetes.
- GLP-1 agonists: g. Tirzepatide (Mounjaro), Semaglutide (Wegovy), Liraglutide (Victoza). A medication for diabetes and weight loss.
- NSAIDs: Anti-inflammatory painkillers – e.g. Ibuprofen, Naproxen, Diclofenac.
What action should I take?
If you develop a dehydrating illness you should temporarily stop the above listed medication. Drink plenty of clear fluids (water or rehydration drinks) in small, frequent sips" while unwell. It is important to restart your medication once you have recovered from the illness, usually after 24-48 hours of eating and drinking normally again. Continue to take them as you usually would and do not take any additional doses for those missed.
Emergency advice: If you are in doubt, or have any concerns:
Please contact your GP practice or NHS 111 to speak to a medical professional for further information and advice regarding your symptoms and medication.
Last updated 05/01/2026