A stomach bug is usually a miserable two days and nothing more. But if you are over 50 and taking regular medication for blood pressure, heart failure or diabetes, those two days can put real strain on your kidneys, and the medicines that keep you well the rest of the year are often what makes that strain worse.
This is what healthcare professionals mean by sick day rules: a short, planned pause on certain medicines while you are dehydrated, then a restart once you are eating and drinking normally. It is one of the most useful conversations you can have with your GP or pharmacist, and one of the least likely to happen unless you raise it.
TL;DR
- Dehydrating illness (vomiting, diarrhoea, high fever) can trigger acute kidney injury, and several common medicines increase that risk.
- The medicines usually paused are ACE inhibitors, ARBs, diuretics, NSAIDs, SGLT2 inhibitors and metformin, remembered as SADMANS.
- TILDA research found 15.6% of Irish adults over 50 have chronic kidney disease, around 226,000 people, and 98% did not know it.
- Restart after 24 to 48 hours of normal eating and drinking, and never double up on missed doses.
- Some medicines run the opposite way: steroids may need increasing, and insulin must never be stopped.
- The HSE National Renal Office publishes a Medication Sick Day Guidance leaflet your GP or pharmacist can complete with your own medicines named on it.
Why a short illness can hurt your kidneys
Your kidneys need steady blood flow and pressure across the filtering units. When you lose fluid quickly through vomiting, diarrhoea or fever, blood volume drops and the kidneys fall back on internal reflexes to hold that pressure and keep filtering.
Several very common medicines block precisely those reflexes. That is not a flaw in the drugs: blocking those pathways is exactly why they protect your heart and kidneys over years. But it means the safety net is switched off when you most need it. The result can be acute kidney injury, a sudden drop in function that is often reversible if caught and much less so if not.
The Irish picture
Kidney disease is far more common than most people realise, and far less visible. Analysis of data from The Irish Longitudinal Study on Ageing (TILDA) found that 15.6% of adults aged 50 and over in Ireland have chronic kidney disease, roughly 226,000 people, and that 98% of them were unaware of it. The Irish Kidney Association puts the figure across the whole population at about one in ten.
Reduced kidney function rarely announces itself: no pain, often no symptom until it is well down. So the takeaway is not “this applies to people with kidney disease”, but that many people in their 50s, 60s and 70s have less kidney reserve than they assume.
Which medicines are usually paused
- ACE inhibitors, ARBs and ARNIs (ramipril, lisinopril, losartan, candesartan, sacubitril/valsartan). These blunt the hormone system that props up filtration pressure when blood volume falls.
- Diuretics, or water tablets (furosemide, bendroflumethiazide, indapamide, spironolactone). They actively remove fluid, the last thing you need when you are already losing it.
- NSAIDs, anti-inflammatory painkillers (ibuprofen, diclofenac, naproxen), including ones bought over the counter. These narrow the vessel feeding the filter.
- SGLT2 inhibitors (empagliflozin, dapagliflozin). Beyond fluid loss, there is a risk of ketoacidosis even with near-normal blood sugars.
- Metformin. If kidney function drops, metformin accumulates, raising the risk of lactic acidosis.
The memory aid used in practice is SADMANS: Sulfonylureas, ACE inhibitors, Diuretics, Metformin, ARBs, NSAIDs, SGLT2 inhibitors. Not every list is identical, which is why yours should be written down.
When the rule applies, and when to restart
Sick day guidance is aimed at genuinely dehydrating illness, not every sniffle. The usual triggers are two or more episodes of vomiting or diarrhoea in a day, fever with sweats and shaking, or not being able to keep fluids down. A head cold with a good appetite does not count.
Restarting is where people get caught out. Resume your usual doses after 24 to 48 hours of eating and drinking normally, and do not take extra tablets to make up for missed ones. Nor should you leave them stopped indefinitely: forgetting to restart a blood pressure or heart failure medicine causes its own harm, quietly, weeks later. If you live alone, set a phone reminder on day one.
The trap: some rules run the other way
This part is worth reading twice, because “sick day rules” is used to mean two opposite things.
If you take long-term steroids such as prednisolone or hydrocortisone, or have adrenal insufficiency, your sick day rule is usually to increase the dose during illness, not stop it. Stopping abruptly can cause an adrenal crisis, a medical emergency.
If you have type 1 diabetes, you must never stop insulin, even if you are not eating. Diabetes sick day rules are a separate set of instructions involving closer glucose monitoring and checking for ketones, and Diabetes Ireland has clear guidance on it.
Anticoagulants, epilepsy medicines and Parkinson’s medicines should also not be interrupted without advice. Which is precisely why a generic list is not enough and a personal plan is.
When to ring someone
Contact your GP or the out-of-hours co-op for your area if you are passing much less urine than normal or none at all, cannot keep fluids down for more than 24 hours, become confused or unusually drowsy, or feel worse rather than gradually better. Confusion in an older adult during an infection is a red flag, not a personality change. For chest pain, severe breathlessness or collapse, ring 112 or 999.
Make the plan before you need it
Nobody makes good decisions about tablets at three in the morning with a basin beside the bed. So do this while you are well:
- Bring your full medicines list, including anything bought over the counter, to your next GP or pharmacy visit and ask: “Which of these should I pause during a vomiting or diarrhoea illness, and when do I restart them?”
- Ask about the HSE National Renal Office’s Medication Sick Day Guidance leaflet, designed for a professional to complete with your own medicines named on it.
- Keep the completed card with your medicines and tell whoever would look after you where it is.
- If you have a medical card or GP visit card and a qualifying condition such as hypertension, heart failure, diabetes, COPD or asthma, your Chronic Disease Management Programme review is a natural place to raise it.
- Your community pharmacist can do this without an appointment, and is one of the most underused free resources in Irish healthcare.
Dehydration is not only a winter gastro-bug problem, either. Hot spells, long days in the garden and travel with an upset stomach all count.
None of this is about fragility. It is the opposite: knowing which two or three of your tablets need a pause during a bad 48 hours protects a large amount of function. At Críonna Health, we think that is what ageing well actually looks like, knowing your own body well enough to make good decisions quickly.
This article is general information and is not a substitute for advice about your own medicines. Never stop or change a prescribed medicine without speaking to your GP or pharmacist.
📷 Photo by Vitaly Gariev on Unsplash
