Medication Sick-Day Rules

Medication sick-day rules describe temporary changes to medicines during an acute illness that causes dehydration, poor oral intake or hypotension. The aim is to reduce the risk of acute kidney injury, lactic acidosis, ketoacidosis, hypoglycaemia and drug toxicity.

They are particularly important in older people and patients with diabetes, chronic kidney disease, heart failure or multiple long-term medications.

💧 What Is a Dehydrating Illness?

Consider using sick-day rules when the patient has:

• 🤮 Repeated vomiting
• 🚽 Significant diarrhoea
• 🌡️ Fever with sweating or rigors
• 🥤 Inability to drink normally
• 🍽️ Markedly reduced food or fluid intake
• 🩸 Hypotension, dizziness or postural symptoms
• 🚱 Reduced urine output or very dark urine

These illnesses reduce circulating volume. Renal perfusion then depends partly on constriction of the efferent arteriole through angiotensin II. ACE inhibitors and angiotensin-receptor blockers impair this compensatory mechanism, while diuretics further reduce circulating volume and NSAIDs constrict the afferent arteriole. The combination can produce a substantial fall in glomerular filtration and precipitate acute kidney injury.

🧠 The SADMANS Mnemonic

The mnemonic SADMANS identifies medicines that commonly require review or temporary interruption during a dehydrating illness.

🟠 S — SGLT2 Inhibitors

Examples include:

• Dapagliflozin
• Empagliflozin
• Canagliflozin
• Ertugliflozin

These should normally be stopped during significant acute illness, dehydration, fasting or markedly reduced food intake. SGLT2 inhibitors increase urinary glucose and water loss and may precipitate euglycaemic diabetic ketoacidosis, in which dangerous ketosis develops despite a normal or only modestly raised blood glucose.

Check blood ketones when clinically indicated, particularly if there is nausea, abdominal pain, rapid breathing, drowsiness or unexpected malaise. SGLT2 inhibitors should not be restarted until the patient is clinically stable and eating and drinking normally.

🔵 A — ACE Inhibitors

Examples include:

• Ramipril
• Lisinopril
• Enalapril
• Perindopril

During hypovolaemia, angiotensin II normally constricts the efferent arteriole and helps preserve glomerular pressure. ACE inhibitors block this response and may therefore worsen acute kidney injury during significant dehydration.

They may be temporarily withheld if the patient is clearly dehydrated, hypotensive or developing acute kidney injury. This is not a reason to stop them routinely for every mild infection.

🟡 D — Diuretics

Examples include:

• Furosemide
• Bumetanide
• Bendroflumethiazide
• Indapamide
• Spironolactone
• Eplerenone

Diuretics may worsen volume depletion, hypotension, renal impairment and electrolyte disturbance. They are commonly withheld temporarily during a dehydrating illness.

🟣 M — Metformin

Metformin should normally be stopped during significant dehydration, severe infection, hypoxia or acute kidney injury.

Metformin is cleared by the kidneys. Accumulation during renal impairment increases the risk of the rare but potentially fatal complication of metformin-associated lactic acidosis. The risk is greatest when renal impairment is combined with tissue hypoxia, sepsis, circulatory failure or liver dysfunction.

🔵 A — Angiotensin-Receptor Blockers

Examples include:

• Candesartan
• Losartan
• Valsartan
• Irbesartan

ARBs affect renal autoregulation in a similar way to ACE inhibitors. They may be temporarily withheld during significant dehydration, hypotension or acute kidney injury.

🔴 N — NSAIDs

Examples include:

• Ibuprofen
• Naproxen
• Diclofenac
• Celecoxib
• Etoricoxib

NSAIDs inhibit renal prostaglandin production and cause constriction of the afferent arteriole. During dehydration, this reduces blood flow into the glomerulus and may precipitate acute kidney injury.

NSAIDs should be stopped during a dehydrating illness and generally avoided in people with acute kidney injury. Patients should also be warned that ibuprofen and other NSAIDs may be present in non-prescription pain and cold remedies.

🟢 S — Sulfonylureas

Examples include:

• Gliclazide
• Glimepiride
• Glipizide

Sulfonylureas stimulate insulin secretion and may cause prolonged hypoglycaemia if food intake is reduced. They should generally be withheld if the patient is not eating, is vomiting or has low blood glucose.

They do not necessarily need to be stopped when the patient is eating normally and blood glucose is elevated. Glucose monitoring and an individual diabetes plan are therefore preferable to automatically stopping them in every illness.

💉 Insulin

Illness commonly increases counter-regulatory hormones such as cortisol, adrenaline and glucagon, raising glucose concentrations and increasing ketone production. A patient with type 1 diabetes can develop diabetic ketoacidosis rapidly if insulin is omitted, even when they are eating very little.

• Continue basal insulin.
• Monitor capillary glucose more frequently.
• Check blood ketones when glucose is raised or the patient is unwell.
• Use correction insulin according to the individual diabetes plan.
• Seek urgent advice for persistent hyperglycaemia or raised ketones.

💊 Other Medicines Requiring Review

SADMANS is useful but not exhaustive. Acute illness may also require review of:

• GLP-1 receptor agonists: withhold if significant vomiting, diarrhoea or inability to eat and drink because gastrointestinal adverse effects can worsen dehydration.
• Lithium: dehydration and renal impairment can rapidly increase lithium concentrations and cause toxicity.
• Digoxin: acute kidney injury may cause accumulation and toxicity.
• Opioids and sedatives: renal impairment can increase drug or metabolite accumulation, sedation and respiratory depression.
• Anticoagulants: do not stop automatically, but review if there is bleeding, severe renal impairment, thrombocytopenia, inability to take medication or an invasive procedure.
• Antihypertensives: review if the patient is hypotensive, dizzy or falling.
• Nephrotoxic antimicrobials: doses may require adjustment according to renal function.

🥤 What Should the Patient Do?

• Drink regularly, using small frequent sips if necessary.
• Consider oral rehydration solution when losses are significant.
• Monitor urine output.
• Monitor blood glucose more frequently if diabetic.
• Check blood ketones when indicated.
• Seek medication advice if unsure which drugs to withhold.
• Keep a written list of the medicines that have been stopped.

▶️ When Should Medicines Be Restarted?

Most temporarily withheld medicines can be restarted when the patient has been eating and drinking normally for 24–48 hours, dehydration has resolved and the patient is clinically stable. Missed doses should not be replaced by taking extra tablets.

Before restarting, consider checking renal function, potassium and blood pressure when:

• The illness was severe or prolonged
• Urine output was reduced
• Acute kidney injury was suspected
• The patient has chronic kidney disease or heart failure
• Several interacting medicines were withheld
• The patient remains hypotensive or clinically dehydrated

🚑 When Is Urgent Medical Assessment Required?

• Unable to retain fluids or medicines
• Persistent vomiting or severe diarrhoea
• Very low or absent urine output
• Confusion, drowsiness or collapse
• Hypotension, severe dizziness or recurrent falls
• Breathlessness, pulmonary oedema or worsening heart failure
• Severe abdominal pain or rapid, deep breathing
• Blood ketones ≥1.5 mmol/L or otherwise elevated according to the patient’s diabetes plan
• Persistent marked hyperglycaemia or recurrent hypoglycaemia
• Suspected sepsis

🧑‍⚕️ Case Example 1: Gastroenteritis and SADMANS

An 80-year-old man with type 2 diabetes, hypertension and chronic kidney disease takes ramipril, furosemide, metformin and empagliflozin. He develops vomiting and diarrhoea and is drinking very little.

Management: Temporarily withhold ramipril, furosemide, metformin and empagliflozin. Assess hydration, urine output, glucose and ketones, and arrange clinical review if symptoms persist or urine output falls.

Reasoning: Hypovolaemia combined with impaired renal autoregulation and continued diuresis creates a high risk of acute kidney injury. Metformin accumulation may cause lactic acidosis, while empagliflozin increases the risk of ketoacidosis.

🧑‍⚕️ Case Example 2: Mild Respiratory Infection

A 67-year-old woman taking losartan and metformin has a mild cold. She has no fever, is eating and drinking normally and has no vomiting or diarrhoea.

Management: Continue her usual medicines.

Reasoning: Sick-day rules are triggered by dehydration or substantial physiological disturbance, not merely by the presence of any infection.

🧑‍⚕️ Case Example 3: Diabetes and Poor Intake

A 54-year-old man with type 1 diabetes develops influenza and cannot eat. His glucose is 15 mmol/L and blood ketones are 1.8 mmol/L.

Management: He must continue insulin, take fluids and follow his diabetes correction-dose plan. Raised ketones require urgent specialist or emergency advice.

Reasoning: Insulin deficiency promotes lipolysis and hepatic ketogenesis. Stopping insulin because the patient is not eating could precipitate life-threatening diabetic ketoacidosis.

🧑‍⚕️ Case Example 4: Heart Failure

An 84-year-old woman with heart failure takes ramipril and furosemide. She is breathless, oedematous and has gained 3 kg, but has no vomiting or diarrhoea.

Management: Do not automatically apply dehydration sick-day rules. She requires assessment for decompensated heart failure and may need continued or increased diuresis.

Reasoning: The purpose of sick-day rules is to protect a volume-depleted patient. Withholding treatment mechanically in a congested patient could worsen pulmonary oedema.

⚠️ Clinical Pearls

• Sick-day rules are primarily dehydration rules, not rules for every minor illness.
• Assess volume status, renal function, blood pressure and oral intake.
• Do not routinely stop insulin.
• Do not routinely stop corticosteroids; patients at risk of adrenal insufficiency may instead require additional steroid cover.
• Do not apply the SADMANS list mechanically in congested heart failure.
• Document which medicines were withheld and give a clear plan for restarting them.

⭐ Key Point

During significant vomiting, diarrhoea, fever or poor fluid intake, temporarily review medicines that worsen dehydration, impair renal autoregulation or accumulate during acute kidney injury. SGLT2 inhibitors, ACE inhibitors, diuretics, metformin, ARBs, NSAIDs and—when food intake is reduced—sulfonylureas commonly require temporary interruption. Most can be restarted after 24–48 hours of normal eating and drinking, but insulin must not be routinely stopped.