Sick day rules: when to pause some medicines during illness

When you have vomiting, diarrhoea, a high temperature or are simply not drinking enough, your blood volume and blood pressure can fall. The kidneys react to that by protecting their own blood supply. Certain regular medicines interfere with that protective response, so a drug that is helpful on a normal day can contribute to kidney injury on a bad one.

The NHS lists dehydration, low blood pressure, blood loss, infection and sepsis as main triggers of acute kidney injury, and notes that long-term use of ACE inhibitors, anti-inflammatory painkillers and diuretics can also contribute. Older adults aged 65 and over, people who have had acute kidney injury before and those recovering from surgery are at higher risk.

The Specialist Pharmacy Service describes temporarily withholding some drug classes after a risk assessment in acute kidney injury, naming antihypertensives, NSAIDs, diuretics and SGLT2 inhibitors. NHS Inform adds ACE inhibitors and angiotensin receptor blockers in its advice for people with chronic kidney disease.

These are classes rather than a universal list of what to stop. Whether a particular medicine belongs on your plan depends on why you take it, which others you take and how your kidneys work. Stopping the wrong medicine can be harmful, for example if a heart or blood sugar treatment is paused without a plan to restart, which is why guidance is personalised rather than a one-size rule.

Healthcare Improvement Scotland, in its polypharmacy guidance, publishes medicines sick day guidance including an interactive tool that creates personalised cards, downloadable printable cards and leaflets for professionals and for patients and carers. It sits alongside its reviews of medicines for frail older adults and its work on cutting avoidable medicine harm.

The practical point is that a pharmacist or prescriber ideally agrees your list in advance, when you are well. You then know which items to hold, what symptoms trigger that, who to ring and when to restart. Illness is a poor time to be making these decisions for the first time.

The MHRA has warned that gastrointestinal side effects of GLP-1 receptor agonists, namely nausea, vomiting and diarrhoea, can cause severe dehydration leading to hospital admission and potentially kidney damage, and advises staying well hydrated by drinking plenty of fluids. This is a reminder that dehydration risk is not confined to the older, better-known classes of medicine.

Anyone taking these or other newer medicines who develops a persistent stomach illness should ask the prescriber or a pharmacist whether any treatment needs adjusting, and should not wait until symptoms become severe.

A sick day plan has two halves. The first covers pausing; the second covers restarting once you are eating and drinking normally again. Guidance for ACE inhibitors and ARBs notes that kidney function and potassium are checked after starting or changing doses and that abnormal results can mean the medicine is stopped and specialist advice sought. If you have been unwell enough to pause medicines, a blood test afterwards may be advised, particularly if you have chronic kidney disease.

Do not assume that paused medicines can be forgotten. Long gaps in blood pressure, heart or diabetes treatment have their own risks, and your prescriber should tell you when to resume.

The NHS advises drinking enough that your urine is pale and regular through the day, especially in hot weather, and consulting a health professional before starting new medicines or supplements. During illness, small frequent sips are often easier to manage than large drinks.

Medicines that are not on a sick day list can still be affected by dehydration. Paracetamol, for instance, is still unsuitable for people with certain liver or kidney conditions according to NHS pages, so a plan should be checked rather than assumed.

Passing very little urine, extreme thirst, nausea, swollen legs or feet, marked tiredness, confusion or shortness of breath may point to acute kidney injury. The NHS advises seeking urgent care or contacting NHS 111 for these symptoms. Do not rely on a written plan if you are deteriorating; get assessed.