The effects of high blood glucose levels are probably what first led you to visit the doctor when your diabetes was diagnosed.

Normally, the human body keeps its blood glucose level very stable (between 4mml – 7.5mmol/L). The body has various systems (regulated by hormones such as insulin and glucagon) to keep the blood glucose level in this range. These systems fail in people with diabetes.

Signs of high glucose levels are:

  • Increased thirst
  • Increased need to pass urine (you my need to get up several times during the night)
  • Tiredness


What causes my blood glucose levels to increase?

    Sickness or injury (including surgery)

    If you are sick or injured your body develops higher levels of hormones to help you deal with the sickness. One of the things these hormones do is stimulate your liver to start making extra amounts of glucose. This is because you need extra energy to fight the sickness, or heal the injury, and become well again.


    This is fine if you don’t have diabetes. Your body simply increases the amount of insulin it makes, moves this glucose into your body cells, and uses it up. However, when you have diabetes you are low on insulin, and you can’t use up all the extra glucose.


    Not enough medication or the wrong type of medication

    If your dose of medication isn’t high enough, or is the wrong type, you may develop high blood glucose levels.


    Not enough exercise

    Having a regular amount of daily physical activity helps your insulin to work better, which helps to keep your blood glucose levels lower. Sometimes when your blood glucose level is high you don’t feel like exercising (because you feel too tired). But if you are well enough this is often exactly the time to start a regular exercise programme.


    Too much food or the wrong sort of food

    If you are eating too much carbohydrate food, or if you are having lots of concentrated carbohydrate (sugary foods or drinks) your blood glucose levels can increase.

    Increasing body weight


    If you become heavier you will need more insulin to maintain healthy blood glucose levels. Cells that store fat (fat cells) are less sensitive to the action of insulin than lean body cells.



    Your body treats stress in the same way as it treats a physical sickness. The result is the same – your blood glucose levels are pushed up. Learn more about managing diabetes and stress.


    When should I worry about high blood glucose levels?

    It is good to aim to have your blood glucose levels in the range (4mmol/L – 8mmol/L) for 80% of the time. Everyone goes high sometimes. A high of up to 14mmol/L every now and then is okay as long as it settles back down again within the day.

    Seek medical advice on your blood glucose levels if they don’t settle down, or if you notice that your blood glucose levels are often high at a particular time of the day. These things may mean that you and your doctor will need to look at adjusting your diabetes medications.

    If your blood glucose levels continue to climb, or if you are very unwell and your blood glucose levels are high, you should seek help. Health professionals usually become concerned if your blood glucose levels are above 17mmol/L and not settling.


    What is the worst that could happen?

    If you have Type 2 diabetes and your blood glucose gets very high you can develop a condition called HONK (hyperosmolar non ketotic coma).


    It is very rare for this to happen but it is a risk if you don’t get treatment for high blood glucose levels. Drinking plenty of unsweetened fluids when you are sick can help prevent this happening.


    How can I manage high blood glucose levels?

    Short-term your doctor may suggest you increase your diabetes medication. Sometimes a change of medication can help, like by transferring from pills to insulin. Don’t feel bad if this happens. Your Type 2 diabetes does not always stay the same. It is a progressive condition. Most people who have Type 2 diabetes eventually come to need insulin.


    In the longer term, you can bring down your blood glucose levels by:

    • Increasing your level of exercise
    • Making sure you eat the right kinds of food
    • Losing some weight


    If your blood glucose is high because you are sick or stressed it is important to deal with the sickness or put in place strategies to deal with your stress. Talk to your family doctor or diabetes nurse educator about this.