Sick Day Rules for Patients

What is the potential problem?

Taking certain medicines when you are dehydrated can result in you developing a more serious illness. The Medicine Sick Day Rules list medicines that should be temporarily stopped during a dehydrating illness.

Which illnesses cause dehydration?

Dehydration is the loss of fluid from your body. Vomiting, diarrhoea, and fever (e.g. high temperature, sweats, or shaking) can make you dehydrated.

If you vomit or have diarrhoea once, dehydration is unlikely. But if you have two or more episodes, you are more likely to become dehydrated and should follow this advice.

Medicines commonly affected

• ACE inhibitors – high blood pressure/heart conditions. Can impair kidney function if dehydrated.
  Examples: names ending in ‘pril’ – lisinopril, perindopril, ramipril.
• ARBs – high blood pressure/heart conditions. Similar kidney effects when dehydrated.
  Examples: names ending in ‘sartan’ – losartan, candesartan, valsartan.
• Diuretics – for fluid or blood pressure. Can make dehydration worse.
  Examples: furosemide, bendroflumethiazide, indapamide, spironolactone.
• Metformin – for diabetes. Dehydration increases the risk of lactic acidosis.
• NSAIDs – anti-inflammatory painkillers. Can damage kidneys if dehydrated.
  Examples: ibuprofen, naproxen, diclofenac.
• SGLT2 inhibitors – for diabetes, kidney disease, or heart failure. Can increase dehydration risk and cause acid build-up (ketoacidosis) if unwell.
  Examples: names ending in ‘flozin’ – canagliflozin, dapagliflozin, empagliflozin, ertugliflozin.

What actions should I take?

• Temporarily stop taking the medicines listed above during a dehydrating illness.
• Restart them 24–48 hours after you are eating and drinking normally.
• Do not take extra doses for missed ones – resume as normal.

Need more information?

Speak to your pharmacist, doctor, or nurse if you’re unsure what to do.