Enjoying the sun is one of the things many people look forward to in the summer. But if you have diabetes, it can be harder to manage your blood glucose (sugar) levels in the hot weather.

How hot weather affects blood sugar levels

Sitting in the sun for long periods may affect your diabetes because you're not being very active, making blood sugar levels higher than usual. On the flipside, if you take insulin to treat your diabetes it may be absorbed more quickly from the injection site in warm weather, and this increases the risk of hypos.

If you're careful about managing your diabetes then there's no reason you can't have fun in the sun like anybody else. We've created some top tips to stay sun-safe this summer. 

Check blood sugar levels

If you usually check your own blood sugar levels, do this more often and be ready to adjust your diet or insulin dose if you take insulin. If you plan on being active in the sun, like going for a swim, eat some extra carbohydrate at your meal before or as an extra snack. Check your levels beforehand and have a sugary snack if your levels are low. Keep something sugary to hand too, just in case.

Keep meters and test strips away from the sun

Extremes of temperature can also affect blood glucose meters and test strips. If you use these, keep your meter and test strips as close to normal room temperature as possible and out of direct sunlight, but don’t refrigerate them as cold temperatures can also lead to misleading results.

General guidance

If you wear a sensor and need to change it, avoid getting any sunscreen on your insertion site. Clean the area thoroughly before applying the new sensor so it sticks properly. The same applies to an insulin pump if you need to change the insertion site.

Be aware your pump reservoir may need changing more frequently due to insulin warming up.

Cover your pump under a towel when sunbathing, to avoid heating of insulin. If your blood sugar levels seem higher for no particular reason it’s possible that the insulin in your reservoir may have been damaged by the heat so consider changing it. 

Store insulin properly

If you take insulin to treat your diabetes, keep a close eye on how you store it so it still works properly. In hot weather, insulin is best kept in the fridge to stop it going above room temperature. If you’re out and about carry your insulin with you in a cool bag, wallet or pouch. 

When damaged by heat, clear insulin generally becomes cloudy and cloudy insulin becomes grainy and sticks in the side of the glass. Insulin that has been exposed to bright sunlight sometimes has a brownish colour. Do not use insulin that looks like this. Speak to your GP or a healthcare professional if you're unsure.

Other diabetes medications, such as tablets usually should be kept as close to normal room temperature as possible. Check the patient information leaflet that comes with your medication for information on how to store it safely.

Stay hydrated

If you’re being active or just relaxing, everyone knows that hot weather will make you sweat. This is your body's natural way of cooling down, but you’ll need to replace the fluids. 

Drinking water or sugar-free soft drinks will help you to stay hydrated. Carry drinks with you and make sure you have regular sips. Becoming dehydrated increases the risk of hyperosmolar hyperglycemic syndrome (HHS) or Diabetic ketoacidosis (DKA).

Other top tips

When you're out and about in the sun, remember to:

• wear long sleeves, loose trousers, a hat and sunglasses with a UV 400 label
• apply suncream to exposed areas of your body 15 to 30 minutes before going out in the sun and reapply every two hours when you’re still outside.  
• if you have neuropathy, you may not be aware of your feet burning, so wear suncream and flip flops, sandals or shoes on hot ground.

Heat exhaustion

Heat exhaustion can develop when the body finds it difficult to keep cool. Symptoms include headaches, dizziness, nausea and vomiting, tiredness, muscle cramps, stomach cramps and pale skin. As some of these could also be due to unstable blood sugar levels, it's important to test regularly.

Heat exhaustion needs immediate treatment. Move to a cool place to rest and sip a cold drink. If left untreated, heat exhaustion can lead to the more severe and potentially life-threatening condition heat stroke, so take action straight away.

Symptoms of heat stroke include confusion, hallucinations, rapid breathing and convulsions, all of which require immediate medical attention.

Is sunshine good for diabetes?

Nice weather can encourage you to get more active and this increased activity can help improve your sensitivity to insulin and help combat problems like heart disease and high blood pressure. 

You just need to think a little more about how you manage your diabetes as being more active can have an impact on your blood sugar levels. Some people with diabetes worry that exercise will make them feel tired or sending their blood sugar low. But with the right preparation there’s no reason why you can’t be more active in the sun. If you’re at risk of hypos always carrying something to treat them. It’s also great for your mental health as it can reduce stress and boost your mood. 

Remember whether you’re taking a stroll on a sunny day or playing frisbee on a beach, these activities may have more of an impact on your blood sugar than they would in colder weather. 

Try to be extra careful with your feet in the hot weather. If you have neuropathy you may not realise how hot the ground is, so it’s important to make sure you’re always wearing shoes or sandals out in the sun. 

Can vitamin D prevent or reduce your risk of type 2 diabetes?

Researchers have been investigating whether taking vitamin D supplements might help or prevent the development of type 2 diabetes. But despite lots of research in this area, the evidence is mixed and the dffects of vitamin D on reducing the risk of type 2 diabetes tend to be small. More research is needed to test whether vitamin D supplements can reduce the risk of developing type 2 diabetes along with well-known measures such as keeping fit. 

But it’s important everyone in the UK – including people with diabetes - takes a vitamin D supplement during winter months as recommended by the government. It helps absorb calcium, which is important for our bones, muscle and teeth and it helps our immune system fight off infections.