Sick Day Rules: Which Medicines to Stop and When

[HOST] Welcome to ClinicaliQ Clinical Essentials. I'm Emma, and with me is Dr Anzal Qurbain, pharmaceutical physician. Today we're covering sick day rules — when patients need to pause their regular medicines during illness. This is one of those topics that sounds simple but has genuinely serious consequences when it's missed. Dr Qurbain, let's start at the beginning. What are sick day rules?

[EXPERT] Sick day rules are guidance for patients on certain long-term medicines about what to do when they become acutely unwell — specifically when they're vomiting, have diarrhoea, a high fever, or are at risk of dehydration. The core message is: some medicines that are completely safe when you're well become dangerous when your body is under that kind of stress.

[HOST] And is this something most patients know about?

[EXPERT] That's the uncomfortable truth — most don't. If someone is on four or five regular medicines for blood pressure and diabetes, there's a reasonable chance nobody has ever sat down and explained this to them. It often falls through the gap between hospital discharge and primary care.

[HOST] So which medicines are we actually talking about? I've heard the acronym SADMANS.

[EXPERT] That's a really useful one. SADMANS stands for Sulphonylureas, ACE inhibitors, Diuretics, Metformin, ARBs, NSAIDs, and SGLT2 inhibitors. If you look at that list, it's an incredibly common combination — someone with type 2 diabetes and hypertension could easily be on metformin, an ACE inhibitor, a diuretic, and an SGLT2 inhibitor all at once.

[HOST] Let's go through the specific risks. Why is metformin a problem when someone is unwell?

[EXPERT] Metformin is normally well tolerated, but it's cleared by the kidneys. When someone is dehydrated — from vomiting or diarrhoea — kidney function drops transiently. If metformin accumulates, there's a risk of lactic acidosis, which is rare but serious. The BNF is clear: hold metformin if there's significant dehydration or acute illness causing fluid loss.

[HOST] What about ACE inhibitors and ARBs?

[EXPERT] Both of these work on the renin-angiotensin-aldosterone system, which is exactly the system your kidneys use to maintain blood pressure and fluid balance during dehydration. If you're volume-depleted and still taking an ACE inhibitor or an ARB, you lose that protective mechanism and the kidneys can go into acute kidney injury. We call this an AKI on CKD if someone already has chronic kidney disease — and it can be severe enough to need hospital admission.

[HOST] And diuretics?

[EXPERT] Diuretics push more fluid out through the kidneys — completely the wrong thing to be doing when you're already dehydrated. They compound the problem significantly. Furosemide, bendroflumethiazide, spironolactone — all should be paused during acute dehydrating illness.

[HOST] Now SGLT2 inhibitors — I know there's something specific and quite serious here.

[EXPERT] Yes, this is the most important one to highlight. SGLT2 inhibitors — dapagliflozin, empagliflozin, canagliflozin — carry a risk of euglycaemic diabetic ketoacidosis during illness. What makes it dangerous is that the blood glucose can be only mildly elevated or even normal, so patients and clinicians can be falsely reassured. The ketoacidosis is real, it's serious, and it can be missed because of that normal glucose. The rule is clear: stop SGLT2 inhibitors at the start of any significant illness and don't restart until the patient is eating and drinking normally.

[HOST] That's striking. A normal blood glucose doesn't mean they're safe.

[EXPERT] Exactly right. The ketone production happens because these drugs shift the body towards fat metabolism even before glucose climbs. Patients on SGLT2 inhibitors should be counselled to check ketones if they become unwell, not just glucose. Some surgeries now have SGLT2 inhibitor checklists for elective procedures for the same reason.

[HOST] What about sulphonylureas?

[EXPERT] Sulphonylureas — glicazide, glipizide — stimulate insulin secretion regardless of what you're eating. If someone is vomiting and not keeping food down, but still taking their sulphonylurea, the risk of hypoglycaemia is significant. They should hold the dose until they can eat normally again.

[HOST] And NSAIDs are on the list too. Why?

[EXPERT] NSAIDs reduce blood flow to the kidneys through prostaglandin inhibition. Combined with dehydration, they're a classic AKI trigger. Most patients think ibuprofen is harmless because it's over the counter, so they might be taking it for the fever or the aches without realising it's the last thing they should be reaching for.

[HOST] So what should patients actually do during illness? What's the practical message?

[EXPERT] The message is: if you're too unwell to eat and drink — vomiting, diarrhoea, or running a significant fever — stop your SADMANS medicines. Carry on taking everything else, particularly things like antihypertensives that aren't on the list, thyroid medicines, antidepressants, inhalers. The sick day rules apply to a specific subset. And if symptoms persist more than 24 to 48 hours, or if they're very unwell, contact their GP or 111.

[HOST] When can they restart?

[EXPERT] Once they've been eating and drinking normally for 24 to 48 hours and feel well again. That's the consistent guidance. There's no need for a blood test before restarting in most cases, though if there's any doubt about renal function, a quick U&E check is sensible — especially in older patients or those with pre-existing CKD.

[HOST] Who specifically needs to be given this counselling?

[EXPERT] Anyone on one or more SADMANS medicines — which in primary care is a substantial proportion of patients over 60. Particularly important are patients on multiple antihypertensives, patients with type 2 diabetes on SGLT2 inhibitors or metformin, patients with CKD, elderly patients who are generally more vulnerable to dehydration, and patients being started on a new SADMANS medicine for the first time.

[HOST] Should there be written information?

[EXPERT] Yes, absolutely. NHS England and the Renal Association both have sick day rules leaflets that are publicly available and designed for patients. They exist in multiple languages. Handing one over at the time of prescribing takes 30 seconds and could prevent a hospital admission. Many practices now add a sick day rules entry to the medical record as a reminder flag.

[HOST] What about carers and family members? If a patient is very elderly or frail, they might not be managing their own medicines.

[EXPERT] Excellent point. If someone's medicines are managed by a carer or family member, the counselling needs to happen with them present. The instructions should also be written in the Medicines Administration Record or equivalent if the patient is in a care home setting. Care homes are a particular risk area — residents are often on multiple SADMANS medicines and acute illness is common.

[HOST] Is there a risk of going too far the other way — patients stopping medicines unnecessarily?

[EXPERT] There is, and it's worth flagging. Some patients hear "stop during illness" and start withholding medicines at the first sign of a sniffle. The threshold is meaningful illness — things that cause genuine dehydration, vomiting, or very high fever. A mild cold with a stuffy nose does not require stopping metformin. The conversation needs to include that nuance.

[HOST] What's your clinical pearl for this topic?

[EXPERT] The most important thing I'd say is this: the majority of patients on multiple blood pressure and diabetes medicines have never been explicitly told about sick day rules. It's not because clinicians don't care — it's because it tends to get crowded out by other consultation priorities. The next time you review someone on ACE inhibitors, metformin, and an SGLT2 inhibitor — ask them what they'd do if they got a bad stomach bug. If they don't know, that's the moment to tell them. It's a five-minute conversation that can prevent a serious hospital admission.

[HOST] That is such a practical takeaway. To summarise today's episode: sick day rules apply to medicines in the SADMANS group — Sulphonylureas, ACE inhibitors, Diuretics, Metformin, ARBs, NSAIDs, and SGLT2 inhibitors. Patients should hold these during significant illness causing dehydration or vomiting, and restart once eating and drinking normally for 24 to 48 hours. The standout risk is euglycaemic DKA with SGLT2 inhibitors — normal blood glucose doesn't mean they're safe. And most patients on these medicines haven't been told this. Thank you so much, Dr Qurbain.

[EXPERT] Thanks, Emma. It's a genuinely important topic and one where a short conversation makes a real difference.

[HOST] That's all for this episode of ClinicaliQ Clinical Essentials. Find us wherever you get your podcasts, and we'll see you next time.