Sick Day Insulin Adjustment: What to Do When You’re Ill

The golden rule

Do not stop insulin completely on sick days.

Even if you are eating less, your body still needs basal/background insulin to prevent dangerous ketone build-up and dehydration. This is especially critical in type 1 diabetes, but also important in insulin‑treated type 2 diabetes.^[1]

Why sugars often rise during fever and infections

When you are sick, your body releases stress hormones (like cortisol and adrenaline) that push sugar up and make insulin work less effectively.

So many people actually need the same or sometimes extra insulin, not less, even if their appetite is reduced.^[1]

What to do immediately at home

Monitor more often

• Check blood glucose every 2-4 hours while you are unwell (including at night if significantly sick).^[3]
• If you have type 1 diabetes (or a history of ketones), check blood ketones or urine ketones when sick, especially if:

  • Glucose stays high (for example > 250 mg/dL / 13-14 mmol/L)

  • You feel nauseated, are vomiting, or have abdominal pain.^[4]

Fluids are “medicine” on sick days

• Sip fluids frequently to prevent dehydration (small, frequent sips if nausea).
• If sugars are high: choose water or sugar‑free fluids.
• If sugars are low or you cannot eat: use fluids with carbohydrate (like oral rehydration solution, clear soups with carbs, or other tolerated carb drinks) as part of your sick‑day plan.

Insulin adjustment

• Basal / long‑acting insulin (background insulin): Usually continue the full dose; do not stop basal insulin.
• Mealtime / rapid‑acting insulin: If you are eating less, the meal bolus may be reduced, but many people still need some insulin because the liver releases extra glucose during illness.
• If sugars are high: Many sick‑day protocols advise extra rapid‑acting “correction” doses based on your usual correction factor or a percentage of total daily dose, especially if ketones are present.

The exact adjustment should follow your individual written sick‑day plan (if you have one) or be guided by your diabetes team (phone/teleconsult if needed).

Red flags: when you should seek urgent help

Seek urgent medical help or emergency care if any of these occur:

• Persistent vomiting or cannot keep fluids down.
• Moderate or high ketones, or ketones rising despite extra insulin.
• Fast or deep breathing, severe weakness, confusion, chest or severe abdominal pain.
• Very high glucose that does not come down with corrections.
• Signs of dehydration: very dry mouth, dizziness, very low urine output.

These may be warning signs of diabetic ketoacidosis (DKA), especially in type 1 diabetes, or hyperosmolar state in type 2.

If the patient is drowsy or unconscious

• Do not give anything by mouth (risk of choking/aspiration).
• If trained and available, use glucagon for suspected severe hypoglycemia and call emergency services immediately.

About “glucose gel/paste in the cheek”:

• In conscious people who can swallow safely, fast‑acting oral glucose (tablets, gel, juice) is standard for treating low sugar.
• In an unconscious person, smearing gels/pastes inside the mouth can be unsafe because of aspiration risk.

Current recommendations emphasise:

• Glucagon (nasal or injectable) outside hospital for severe hypoglycemia.
• IV dextrose in hospital settings.

So for unconsciousness, the safest message is: Glucagon and emergency help, not oral intake.

Special note for type 2 diabetes patients on tablets plus insulin

During acute illness, some non‑insulin diabetes medicines may need temporary stopping, especially if:

• You are dehydrated.
• You are not eating.
• There is risk of kidney stress or DKA‑like illness.

Key examples:

• SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin, etc.) - often advised to be withheld on sick days because of risk of euglycemic DKA.
• Metformin - may be held if you are significantly dehydrated, have vomiting/diarrhea, or risk of acute kidney injury.

This should follow a clear “sick‑day medicines list” from your doctor (often taught using the “SADMAN” or similar mnemonic in UK/Australia guidance).

Simple takeaway patients remember

• Being sick does not mean you should stop taking insulin.
• Sick day means more glucose/ketone checks, more fluids, and usually continue (or sometimes increase) insulin, especially basal.

If vomiting, ketones, or worsening weakness appear: seek urgent care, don’t wait.