Diabetes in Hot Weather

Fluids and their importance in diabetes.

In the current hot weather, it is possible to become dehydrated as we sweat more. Even a small fluid decrease of 2% can reduce the body’s ability to perform by affecting concentration and capacity to remember. Other affects of dehydration include fatigue, constipation and circulatory problems.

The groups most affected by a fluid decrease are the very young and the elderly.

Dehydration can be a problem in both of these groups because children’s feeling of thirst is not developed enough and with older people the thirst mechanism is declining.

Water is an essential part of life. The amount we need depends on our age, weight, diet, activity levels and climate.

It will vary from person to person but on average most adults need at least 1.5 to 2 litres of fluid daily (approx 3½ pints)

Water makes up a very large part of the body for men about 60-70% of their body weight and women about 55-65% of their body weight.

Blood is 83% water, muscles are 75% water, the brain is 74% water and bone is 22% water.


The types of fluids to be discussed in the article are

  • Water
  • Tea and coffee
  • Milk and Soya beverages
  • Diet drinks
  • Sweetened drinks
  • Fruit juices, vegetable juices and smoothies
  • Cordials and bottled waters
  • Sports drinks
  • Alcohol


Diabetes Ireland recommend water as the best source of hydration.

A lot of the other fluids listed will contain carbohydrates. Carbohydrates (CHO) are made up of sugars and starches and when carbohydrates are digested they are all broken down to sugars (glucose)

It is important to remember it is the total amount of CHO that the person with Diabetes eats or drinks at one time that will have the biggest affect on the glucose level in the blood as the more CHO eaten or drunk will require more insulin.

Fluids containing carbohydrates will be absorbed a bit quicker into the blood stream and this is important to remember when choosing drinks between meals and also the amount of CHO of the total meal.

Tea and Coffee

These can be used towards fluid intake, they do not raise glucose levels to any great extent unless coffee is made with milk or sugar is added to the hot drink.

Tea can have an antioxidant effect.

Coffee should be taken in moderate amounts only, no more then 300mg per day (see table= below)

Approx caffeine contents of some products

  • Cup of instant coffee 75mg
  • Cup of tea 50mg
  • Can of Coke up to 40 mg
  • Mug of coffee 100mg
  • Can of stimulant drink 80mg
  • Bar of chocolate up to 50 mg




Good source of calcium which have been shown to help reduce blood pressure. Most of the general population need 3 servings of dairy products, its 5 for children aged 9-12 and teenagers daily, this equates to 200mls milk, 125g pot yoghurt or 2 thumbs(25g) of hard or soft cheese. Full fat and low fat/diet have the same amounts if calcium.

Milk will affect blood glucose as contains approx 5g CHO for every 100mls so remember to take this into account if you are taking insulin or make changes to your diet.

Soya drinks

Generally used in allergies for example lactose (milk sugar) intolerance or with vegans. Have been shown to improve cholesterol if over 25g is taken daily. Most soy milks only contain approx 4g of this soy protein in 100mls so it is difficult to achieve this quantity daily. Soy products have a low CHO content so do not raise the glucose levels unless of course they are sweetened so best choices are those which are unsweetened and which have added calcium.

Diet drinks

These are usually carbonated and can be labelled diet/light or zero carbs.

Always check the label, it needs to say sweetened with artificial sweeteners. Remember to look at CHO content on the label and if states contains less than 0-2g per 100mls then the product will have little effect on the blood glucose reading.


Usually described as intense or bulk. Intense sweeteners are very sweet so small quantities needed and contain none or very few calories. Examples are Acesulfame, aspartame and saccharine which can be found in Canderel or Hermesetas. Bulk sweeteners also have fewer calories than sugar but can provide bulk so are usually recommended for cooking examples are sorbitol, mannitol and sucralose.

Polyols (sugar alcohols) for example sorbital have a laxative effect and this must be noted on the label.

Foods labelled ‘diabetic’ for example chocolates and sweets are not recommended by the Diabetes Ireland.

EU law states that sweeteners must be authorised before used in food products and these all have an acceptable daily intake level of which there is a large safety margin built in.

Sweetened drinks

Examples are fizzy drinks which are not diet; these are linked with increasing obesity especially in children.

These will also raise blood glucose levels quite quickly as there is about 10g of CHO per 100mls, this is the same as about 8 spoons of sugar in a 500ml bottle.

They are also not a very good source of nutrients. These should be avoided by people with Diabetes unless they are used to treat a hypo (low blood glucose).

Fruit and vegetable juices and smoothies

These can be a good source of minerals and vitamins.

Juices usually contain about 10g CHO per 100mls so will raise blood glucose levels quickly as do smoothies which can contain up to 15g CHO per 100mls.

Best to have with a meal and avoid between meals unless to treat a hypo.

The Dept of Health and Children recommend 5-7 portions of fruit and veg daily but a serving of fruit juice or smoothie(150mls) will only count as one of those servings in a day.

Try to choose pure fruit juices and avoid those with no added sugars.

Cordials and bottled waters

Choose dilutable drinks with no added sugars for example no added sugar Miwadi, Kia-Ora and Robinsons or the supermarkets own brand.

These will not affect blood glucose levels as contain less than 2g CHO per 100mls.

Bottled waters and those sweetened with artificial sweeteners will also not affect glucose levels.

Sports drinks

These are designed to help athletes rehydrate, tend to have a lower CHO content than sweetened drinks but will have extra potassium and sodium.

These will affect blood glucose levels and are not recommended for non athletes as will lead to weight gain and also due to higher salt content.



As for people without Diabetes there are recommendations about safe upper limits.

No more than 17 units or standard drinks are encouraged for men or no greater than 11 units for women.

1 unit equals a half pint of beer or lager, 125mls of wine, and a pub measure of spirits equals 1½ units of alcohol.

Remember all alcohol is high in calories and needs to be reduced if weight loss is required. For a person with diabetes it is also encouraged never to drink on an empty stomach as alcohol has a hypoglycaemic affect.

It is better to have a drink with a meal and no more than 2 at a time.

It is important to have a snack before bedtime if you are on insulin or certain medications (check with your diabetes team) Use diet mixers with spirits.

Visit also drinkaware.ie



  • Remember how important fluids are and we need at least 1½- 2 litres daily on average and people usually require more on sunnier days
  • Fluids will affect blood glucose levels if contain CHO.
  • Best to take juices and smoothies with a meal or snack and limit to once daily
  • Diet drinks, water, no added sugar dilutable drinks and tea/coffee are OK to take between meals.
  • Only take sweetened drinks if blood glucose levels are less than 4 mmols
  • Do not exceed alcohol recommendations.


More information is available on labels on the INDI website www.indi.ie

Or contact the Diabetes Ireland on www.diabetes.ie or 01 842 8118

If you have specific queries on carbohydrate content or suitability of fluids contact your dietitian.