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DIABETES SERIES · ARTICLE 10 OF 17

Sick day rules

Managing diabetes when you're ill.

Most diabetics are taught how to manage their condition on a normal day. Very few are taught what to do when they're sick. So when the flu hits, or a stomach bug, or COVID, or any of a hundred other infections — blood sugar goes haywire, eating becomes hard, medication routines get confused, and people end up in hospital for problems that were entirely avoidable.

This article gives you the sick day rules — a set of simple principles that protect you from a bad week becoming an emergency. Print this. Put it on the fridge. Make sure someone in your household knows it too.

Before you read on

These rules apply to short illnesses — flu, colds, stomach bugs, urinary infections, COVID-19, chest infections, gastroenteritis. For major illness, planned surgery, or anything serious, your medication plan should be adjusted in advance by your clinic or doctor.

Why illness affects blood sugar

When your body fights an infection, it releases stress hormones (cortisol, adrenaline, glucagon). These hormones raise blood sugar, sometimes dramatically. Your body is doing this on purpose — it wants more fuel available for the immune fight — but in a diabetic, the result can be very high readings.

At the same time, illness often means eating less, drinking less, throwing up, or having diarrhoea. So blood sugar can swing both ways:

• Stress + infection → high blood sugar (the more common pattern)

• Vomiting + not eating → low blood sugar (especially if you've taken insulin)

Sick day rules manage both possibilities.

The seven sick day rules

Rule 1 — Do not stop your diabetes medication

This is the rule people get wrong most often. When you stop eating, the instinct is to stop taking insulin or tablets. Don't. Your body still needs medication to handle the high blood sugar that illness causes — even if you're not eating.

Specific guidance:

• Long-acting (basal) insulin: do not stop. May even need to be increased — ask the clinic.

• Short-acting (mealtime) insulin: may need to be reduced if you're not eating, but rarely stopped.

• Metformin: stop temporarily if you are vomiting, have diarrhoea, or can't drink fluids — it can cause problems in dehydration. Restart when eating and drinking normally.

• SGLT2 inhibitors (empagliflozin, dapagliflozin, etc.): STOP during acute illness, especially with vomiting or fever. They can cause a serious complication called euglycaemic DKA.

• Sulfonylureas (glibenclamide, gliclazide): may need to be reduced if you're not eating to avoid hypoglycaemia.

If you're unsure, phone the clinic. A 5-minute call is far better than a guess.

Rule 2 — Drink more water

Dehydration is the silent killer of sick day management. High blood sugar makes you urinate more. Fever makes you sweat. Vomiting and diarrhoea cost more fluid. All of these reinforce each other.

Aim for at least 3 litres of sugar-free fluid across the day — water, rooibos tea, clear soup, sugar-free cold drinks. Sip throughout the day even if you don't feel thirsty. Thirst is a late signal.

Rule 3 — Test blood sugar more often

On a normal day you might test once or twice. On a sick day, test every 2 to 4 hours, including overnight if it's a bad day. This is how you catch trouble early instead of finding out at 3 AM.

Especially test:

• Before meals (even if you're not eating much)

• Before bed

• If you feel worse

• If you've taken extra insulin

• After any vomiting or diarrhoea

Rule 4 — Keep some carbs going in

Even if you can't face a meal, your body needs some carbohydrate to work with. Aim for about 15 g of carbs every hour. Small amounts, frequent, easy on the stomach:

• Plain crackers or dry toast (a slice = \~15 g carbs)

• Soup with a roll

• Plain rice or porridge

• Half a banana

• Half a glass of fruit juice

• Custard, jelly, ice cream (yes, really — easy carbs on a bad day)

• Plain biscuits (Marie biscuits, Tennis biscuits, oat biscuits)

• Sugary cold drink (yes, today — see callout)

Sugar is your friend when you're sick and not eating

On a normal day, sugary cold drinks are off the menu. On a sick day when you've taken insulin and can't keep food down, a glass of regular Coke or fruit juice is a useful medicine. It gets carbs in fast, prevents low blood sugar, and is easy to swallow.

The rule reverses temporarily because the priorities reverse. Return to normal rules once you're eating again.

Rule 5 — Check for ketones if Type 1 (or insulin user with high readings)

Ketones are a chemical your body makes when it can't use glucose for fuel and turns to fat instead. In normal small amounts this is fine. In large amounts — especially with high blood sugar and dehydration — they cause diabetic ketoacidosis (DKA), a life-threatening emergency.

Check ketones using urine ketone strips (Ketostix, available at any pharmacy for around R100) if:

• You have Type 1 diabetes and blood sugar is over 15 mmol/L

• You feel nauseated or are vomiting

• Your breath has a fruity smell

• You're deep-breathing without exercising

• You feel confused or extremely tired

If ketones are moderate or large — get to a hospital. If ketones are present and blood sugar is also high, this is the most urgent diabetic emergency outside of severe hypoglycaemia.

Rule 6 — Have a sick day box ready before you need it

Don't shop for sick day supplies when you're already sick. Keep a small box at home with:

• Glucose tablets or sweets (for low blood sugar)

• Ketone testing strips (within expiry date — they don't last forever)

• A thermometer

• Paracetamol (safer than NSAIDs for kidneys)

• Oral rehydration salts (Rehydrat or Energade) — for vomiting and diarrhoea

• Plain biscuits, soup sachets, custard

• A few cans of sugar-free cold drink

• A printed copy of these sick day rules

• The clinic's phone number

Rule 7 — Know when to call for help

Call the clinic the same day if:

• Blood sugar is consistently over 15 mmol/L for more than 24 hours despite normal medication

• Blood sugar is consistently under 4 mmol/L despite eating fast sugar

• You can't keep any fluids down for more than 6 hours

• You have moderate ketones (if testing)

• Symptoms of illness are getting worse rather than better after 48 hours

• You're not sure what to do

Go to a hospital immediately if you have any of these

Vomiting that won't stop

Blood sugar over 20 mmol/L with vomiting or confusion

Moderate or large ketones with any symptoms

Fruity-smelling breath

Rapid, deep breathing

Confusion, drowsiness, or inability to wake the person properly

Severe chest, abdominal, or back pain

Difficulty breathing

A young child or older adult with any of the above — go faster, not slower

Special situations

Vomiting and diarrhoea

If you can't keep food or fluids down, blood sugar can drop fast (especially on insulin). Sip small amounts (a tablespoon every 5 minutes) of:

• Flat regular cold drink (let the fizz out)

• Oral rehydration solution (Rehydrat, Energade)

• Thin soup

• Diluted fruit juice

If you can't keep down even small sips for more than 4 to 6 hours, go to a clinic or hospital — you may need a drip.

Fever

Fever raises blood sugar dramatically. Use paracetamol every 4 to 6 hours to bring it down (avoid NSAIDs like ibuprofen when possible because of kidney load). Cool yourself with damp cloths if needed. Test blood sugar more often during fever.

Urinary tract infection

Often the first sign in older diabetics is a sudden rise in blood sugar with no obvious cause — sometimes before the usual UTI symptoms (burning, frequency). If readings are unusually high for no clear reason and you have any urinary symptoms, get checked. Untreated UTIs in diabetics can spread fast.

COVID-19 and chest infections

Both raise blood sugar significantly and can cause complications faster in diabetics. The general rules apply, plus: monitor breathing rate. If you're short of breath at rest, can't speak in full sentences, or your lips look blue, go to a hospital.

Going for planned surgery

Tell the surgical team you have diabetes and what you take. They will usually adjust your insulin or tablets for the day of surgery. Don't make changes without their guidance. Carry a written list of your medications.

The bigger picture

Sick day rules are the difference between a bad week that you ride out at home, and a hospital admission that could have been prevented. They are not complicated. The main thing is having a plan ready before the sickness hits, because in the middle of a flu — fevered, tired, confused — is not the time to learn this.

The next article in this series steps back from the day-to-day and looks at long-term complications more broadly — the eyes, the kidneys, the heart — what to watch for, what tests to ask for, and what the trade-offs really are.

Where to get more help

Diabetes South Africa — diabetessa.org.za · 011 792 9888

In an emergency — 10177 for an ambulance, or your nearest hospital emergency department

Phila Today Diabetes Series — next: the long-term complications nobody wants to talk about

Phila Today · Article 10 of 17 in the Diabetes Series