Diabetes medicines on sick days and in hospital

When the body fights infection or recovers from injury it releases stress hormones that raise blood glucose and make insulin less effective. At the same time, vomiting, diarrhoea or fever can cause fluid loss, and eating may fall. The result is a mix of high sugars and dehydration, sometimes with a risk of low sugars if you take glucose-lowering drugs but eat little.

The NHS lists illness, injury, surgery and inadequate insulin among causes of diabetic ketoacidosis, which affects mainly people with type 1 diabetes but can occur in insulin-treated type 2. Good sick-day habits are about preventing that, and avoiding dehydration.

The NHS says never to skip insulin even when not eating, to monitor blood glucose regularly, to test for ketones when glucose is high or when ill, and to follow the sick-day protocol provided by your care team. Insulin may need to go up, not down, during illness, but the adjustment should come from your plan or from a call to the team.

Drink fluids regularly, aim to keep up carbohydrate intake with sugary drinks or easy foods if you cannot eat meals, and check readings more often than usual. Write down times and results to share with a nurse by phone. Many teams give written "sick day rules" at diagnosis; ask if you do not have a copy.

• Test blood glucose more often than usual, as your plan advises.

• Test ketones if glucose is high or you are unwell.

• Keep drinking fluids and, if you cannot eat, take carbohydrate as a drink.

• Phone the diabetes team or NHS 111 early rather than waiting for symptoms to settle.

The NHS pages for metformin and dapagliflozin both say that if you get ill with vomiting, diarrhoea or a high temperature there is a risk of dehydration and to talk to a pharmacist or doctor. Sick-day guidance in many UK services recommends temporarily pausing certain medicines when dehydrated, but which ones, and for how long, is for your own team to say. Diabetes medicines can be grouped as follows.

Gliclazide and other sulphonylureas can cause low blood sugar if meals are skipped; the NHS says not to skip or delay meals and to treat a hypo with something sugary. Dapagliflozin lists ketoacidosis among serious side effects, with extreme thirst, confusion, unusual tiredness or fruity-smelling breath meaning contact NHS 111. The NHS adds that metformin and alcohol together raise the risk of serious side effects.

• Insulin: keep taking it; adjust only as your plan or team advises.

• Metformin and SGLT2 inhibitors such as dapagliflozin: ask whether to pause while dehydrated.

• Sulphonylureas: take care if eating is reduced because of the hypo risk.

• Blood pressure and kidney-related medicines: your team may also advise a temporary pause when dehydrated.

The NHS says DKA symptoms usually develop over 24 hours, sometimes faster. They include great thirst, passing a lot of urine, stomach pain, nausea or vomiting, diarrhoea, deeper breathing, breath that smells fruity, tiredness, drowsiness, confusion and blurred vision.

The NHS says to call 999 or go to A&E for blood ketones above 3 mmol/L or urine ketones 2+, or for DKA symptoms when ketone levels are unknown. It says to call the diabetes team or NHS 111 for ketones of 0.6 to 1.5 mmol/L with feeling unwell, for 1.6 to 3 mmol/L, or for high glucose that is not falling with insulin.

Whether you are admitted for diabetes or something else, tell staff immediately that you have diabetes, give them your medicine list and ask for the inpatient diabetes team. Fasting before a procedure, steroids, infection and drips can all change glucose, and the team may use a variable-rate insulin infusion or adjust your regular doses.

Insulin should not simply be left out because you are nil by mouth: that is how ketoacidosis starts. If you normally manage your own insulin or use a pump or sensor, ask whether you can continue under the ward policy. Keep hypo treatment on the locker and make sure staff know how you feel when your sugar is low.

Check that the discharge letter lists any changed doses, new medicines and restart instructions for paused tablets, and arrange follow-up with your GP or diabetes team. Steroid courses and infections can leave sugars high for days.

The WHO fact sheet lists insulin, metformin, sulphonylureas and SGLT-2 inhibitors among type 2 treatments, and many people also take blood-pressure medicines and statins. Our guides on type 1 and type 2 diabetes cover long-term care, and the page on Ramadan covers another period when medicines need planning.