Heatwaves are becoming more common in the summer months and with Type 1 Diabetes, handling hot weather takes a bit more effort. Glucose levels can trend low when body temperature increases or level can trend high when dehydration occurs. Insulin and test strips denature in hot weather or when directly exposed to sunlight for a significant period of time and heat exhaustion is more common in those with Type 1 Diabetes.

Prevention in four steps

It’s much more sensible to prevent dehydration, heat exhaustion, hypoglycemia and hyperglycemia.

Step 1: Limit sun exposure

Like everyone else, be sensible about sun exposure. Stay indoors (or at least in the shade) between 11am – 3pm, drink plenty of water, wear sunscreen, light coloured clothing, sensible shoes and a hat and also check your blood glucose levels more often. Be aware that outdoor shade or clouds doesn’t protect you fully form the sun – reflected and filtered sunrays are still a potential problem – so wear sunscreen outdoors and reapply every 2 hours or after swimming. Limit exercise during the hottest periods or visit the local pool or air-conditioned gym for a workout. Alternatively, exercise first thing in the morning before the hot weather arrives.

Step 2: Store your supplies safely

Test strips and insulin are damaged by high heat. Stash your supplies in the coolest room in the house away from direct sunlight. Keep spare insulin in the fridge (as always). Carry spare supplies in an insulated case and never leave them in a hot car. Never expose insulin or test strips to direct sunlight for long periods of time. Keep your pump and tubing protected beneath your clothes.

Step 3: Create a cool environment

Keep windows, blinds and curtains shut upstairs in bedrooms during the day then open windows during the night. Also keep curtains drawn downstairs when not home, particularly in south facing rooms. Grow your own shade. Strategically placed decidious trees and shrubs add much shade and further reduce indoor and garden temperature whilst allowing plenty of sun through in the winter.

Finally, create a super cool room at home. Pick the coolest room in the house (usually basement/ground floor, north facing rooms are coolest). Insulate it well – things like reflective window film can reduce indoor temperature by up to 6 degrees without restricting views or severely restricting light entering the room. Invest in a fan, ceiling fan or if need be, air conditioning unit to keep it cool.

Step 4: Spend days out at place with plenty of shades and/or air-conditioning.

We have a list of places that are always cool when home begins to feel cooped up. A walk in the forest, swimming at the local pool, visiting places like the New Forest Wildlife Park where even a large part of the play area is in shade, are some of our favourite things to do on a hot weekend. Many National Trust properties, particularly the large Estates like Mottisfont, Stourhead and Kingston Lacy have heavily shaded areas to enjoy.

Shady adventure playground at New Forest Wildlife Park

Heat and hypoglycemia

A high body temperature and warm skin can lead to an increase in insulin absorption and efficiency, which in turn can cause hypoglycemia and glucose levels that remain perpetually quite low. It’s important to pay closer attention than usual and take appropriate action (the same thing you always do – lower insulin/have some carbs) to prevent and treat hypoglycemia.

It may become more challenging to detect hypoglycemia. Symptoms of even mild heat exhaustion can mask hypoglycemia, we find that the CGM drops out more frequently as the adhesive loosens in hot weather. Also be aware that extreme heat can damage test strips which will then render inaccurate results – usually falsely elevated levels, which could be disastrous if a correction bolus is given when someone is already have issues with hypoglycemia.

Heat and hyperglycemia

Dehydration is common, particularly in children, during hot periods. Dehydration can cause hyperglycemia, particularly when overheating is happening – traveling in hot vehicles, spending hours in hot offices and classrooms, remaining in direct sunlight for extended periods, exercising in the sun during hot weather spells and so on. It’s important to recognize and address the symptoms of dehydration, but even more importantly, drink plenty of fluids to prevent dehydration.

Symptoms of dehydration:

  • Thirst
  • Less-frequent urination
  • Dry skin or dry mouth
  • fatigue and lethargy
  • feeling lightheaded, faint or dizzy
  • Increased heart rate and breathing
  • Confusion

What to do

  • Drink plenty of fluids. Ideally, stick with water (or homemade sugar free ice-tea), varied – if you have to – with some diluted low-carb squash.
  • Avoid carbonated, caffeinated, alcoholic, sugary and hot drinks.
  • Once dehydrated, an oral rehydration solution – available from pharmacies – will be needed. Be aware that by default glucose-containing solutions are provided, but carb-free solutions are available – check with your pharmacist.
  • Seek immediate medical assistance for severe dehydration.
  • Test glucose levels more frequently and treat hyperglycemia as you normally would.

 Heat exhaustion and heatstroke

Heat exhaustion and heatstroke usually happen during particularly hot spells. Type 1 Diabetes carries a higher risk of developing heat exhaustion. Know the symptoms of heat exhaustion and heatstroke, take steps to prevent it and act quickly if it does happen.


The symptoms of heat exhaustion are very similar to those of hypoglycemia. Heat exhaustion can, therefore, mask episodes of hypoglycemia or conversely, can be mistaken for hypoglycemia. If left unaddressed, heat exhaustion can progress to heatstroke, a much more serious condition that could be life-threatening.

Heat exhaustion also looks very similar to a migraine in children and young adults (who often do not have unilateral pain or aura symptoms) and could be mistaken for a migraine in those who have the condition. The distinguishing features of heat exhaustion is muscle cramps, rapid pulse and lowered blood pressure, but these may not always be present.

If unsure, taking action as if someone has heatstroke does no harm, as long as the alternative causes are not excluded. (i.e. treating someone for heatstroke for 30 minutes when they are hypoglycemic could lead to very serious consequences if hypoglycemia is left untreated.) None of the actions taken for heatstroke would impact negatively on either hypoglycemia, hyperglycemia or a migraine.

  • fatigue and lethargy
  • feeling lightheaded, faint or dizzy
  • headache
  • nausea and vomiting
  • thirst
  • urinating less often and having much darker urine than usual
  • muscle cramps
  • rapid pulse
  • lowered blood pressure
  • sometimes heavy sweating (*can be absent in those with Type 1 Diabetes who may sweat less)

What to do

If someone has signs of heat exhaustion:

  • Move them to a cool place. North facing rooms, lower floors, air-conditioned rooms or somewhere in the shade is usually the coolest.
  • Make them comfortable – loosen tight clothing, remove as much of their clothing as is appropriate and have them lie down
  • Drink plenty of water. If glucose levels are trending low, mixing in some fruit juice could be helpful, whilst if levels are trending high, stick to carb-free, non-caffeine, non-alcoholic fluids.
  • Cool their skin – use a cool, damp cloth, pack cold packs around the hottest part of the body (take care not to place ice near cannula sites or CGMs as extreme cold could damage them or affect insulin absorption). If possible, fan damp skin. If at home, have a cool shower then retreat to the coolest room in the house and turn on a fan.
  • Stay with them. Symptoms should drastically improve within 30 minutes. If it doesn’t, seek medical advice.

Call 999 for an ambulance if the person at any point has severe symptoms, such as loss of consciousness, confusion or seizures.

The NHS has an information sheet here on heat exhaustion and heat stroke with relevant information. Additionally, the Met Office issues heatwave warnings for the UK here.