Hyperglycaemia or high (or hyper) as it is often called, means a higher than normal level of glucose in the blood; typically above 15mmol/l. You should always check for ketones in your blood or urine if you have a very high level of blood glucose. If your tests show ketones in two or more tests in a day or if you feel unwell (e.g. if you feel sick, vomit, or become drowsy) you should seek medical advice. Highs, especially if combined with ketones in the urine, are more dangerous than hypoglycaemia, as they can lead to the very dangerous situation of diabetic ketoacidosis (for more information see Diabetes UK website).

Symptoms of hyperglycaemia

Symptoms of highs are the same as those of untreated diabetes: thirst, frequent urination (peeing) and tiredness. If the symptoms go on for a long time they can cause weight loss and blurred vision. The most common reasons for highs are: not enough insulin, infection or illness, less exercise than usual, eating or drinking too much carbohydrate and sudden excitement or stress.

Having persistently high blood glucose levels will avoid hypos but it will increase the risks of developing complications of diabetes. When complications do arise the organs most likely to be affected are: eyes, kidneys, peripheral nerves in the hands, legs and feet, the skin and large blood vessels. There are effective treatments for these problems so long as they are picked up early. This is one reason why it is so very important to attend for regular medical check-ups.

Maintaining a well controlled and stable blood glucose level is sometimes very difficult for people on insulin. Some people have what is known as brittle diabetes where control is particularly difficult to achieve. If you are having troublesome hypos followed by high blood glucose levels you need to contact your diabetes care team because it means that your insulin regimen is not working and you might need to change your insulin or adjust the dosage.

Many young people said that they found it easier to recognise hypo symptoms rather than highs particularly when their blood glucose is only moderately high. The problem is that damage to blood vessels does start even with moderately high blood glucose levels - you don't need to 'feel high'. This is the reason why you need to do frequent blood glucose testing and cannot rely just on how you feel.

Learning to control highs

Some young people indicated that they have had very few highs (or hypos) since diagnosis and attributed it to checking their blood glucose levels several times during the day particularly around meal times. One young woman said that her blood glucose result could then be use by her as a guide as to how much carbohydrate she needed to eat at that particular meal. One young man who was diagnosed at the age of 16 initially had a period of high blood glucose levels but followed the advice from his consultant and eventually his levels became more stable.

She finds it hard to explain how she feels when she is high. Says that she 'hate' being high and that she hasn't being high for years.

She has had very few highs (or hypos) and uses her blood glucose test result as a guide as to how much carbohydrate she needs to eat at each meal.

He understood that after diagnosis his blood glucose levels would take time to settle and followed his consultant's advice to do glucose tests, insulin & regular meals.

Young people said that one common reason why they go high sometimes is that they do not inject or have not injected enough insulin to cover what they have eaten. Some young people on analogue type of insulin said that they might not inject if they are having 'just' a snack or if they wake up late. Another situation is missing mid-day injections at school. (See also 'Insulin: Doing injections everyday' and 'Diet and diabetes'). Some young people indicated that drinking sugary alcoholic drinks such as Alcopops have sent their glucose levels sky high (for more see 'Drinking and alcohol').

They talk about those situations in which they might not inject and end up with high blood glucose levels. But they understand the importance of injecting insulin.

The young people we talked to said that if they have a series of high results they will try and find the reasons for it - maybe they ate more or different foods than usual, they had sugar without realising it or, their carbohydrate/insulin ratio was insufficient, they are working overtime or revising for exams and not doing as much physical activity as usual. In general, they tend to go high when they do things outside their normal routine. 

Describes how he feels when he is high and the possible reasons for it. Says that it is a good idea to keep a diabetes record book, but he doesn't do it because he is lazy!

Young people said that running high blood glucose levels would make you feel miserable, angry and depressed. Many talked of feeling lethargic and unable to concentrate during school lessons. Young people suggested that the teenage years are the worst when it comes to control blood glucose levels.

His blood glucose levels used to be very high and this affected his mood. Once he became violent and since then he has worked hard at keeping them down.

Says that high blood glucose levels made her feel depressed and that her diabetes doctor has changed the type of insulin and the number of injections per day.

A number of young people indicated that they have or had preferred their blood glucose level to be a bit higher rather than lower because they did not want to risk having a hypo in front of friends or at school or when they are by themselves, particularly if they have had experiences of going very low and losing consciousness.

He preferred to have his blood glucose levels a bit high when he was by himself because he was scared of having hypos.

Checking for ketones

Some young people said that it is a good idea to check for ketones if you have high blood glucose levels; that it is not a good idea to leave it untreated because in extreme cases it can lead to diabetic ketoacidotic coma. One young woman recently discovered ketosticks and checks her urine for ketones whenever she thinks she has high blood glucose levels. Another young woman who has had several episodes of ketoacidosis (DKA) has been told by her nurse what to do if she finds ketones in her urine.

She has a blood meter that advises her to test her urine for ketones when her blood glucose reading is higher than it should be. Says that you can get keto sticks on prescription.

If she finds ketones in her urine she drinks plenty of water and has been able to get rid of them without calling her nurse. She still worries if her blood glucose levels go high.

Some young people we talked to used not to inject insulin on a regular basis and consequently, used to run high blood glucose levels for long periods of time. In their experience they have found that bringing their blood glucose levels down again is not easy, that it can be very difficult both physically and emotionally because even insignificant drops in blood glucose levels can produce hypo type of warning symptoms.

When she started injecting insulin regularly again she experienced hypos-type of symptoms even though her blood glucose levels were still significantly high.

High blood glucose levels and complications

Having persistently high blood glucose levels will increase the risks of developing complications of diabetes. Several of the young people we talked to have developed diabetes-related complications as a direct result of having high blood glucose levels for years. One young woman developed complications that lead to her been registered blind at the age of 23. Another young woman has developed a skin complication called scleroderma diabeticorum and doctors have also found that the tiny blood vessels in her eyes are leaking. 

After years of having high blood glucose levels she developed diabetes-related complications that have affected her eyesight.

Her skin and eyes have been affected by high blood glucose level. Says that these were wake up calls and her control has significantly improved.

A young woman indicated that doctors tend to talk much more about hypos and its complications but feels that highs can be potentially dangerous and not enough emphasis and advice is given to teenagers on this subject.

Says that there is not enough awareness about the dangers linked to highs; that doctors emphasised hypos and neglect highs.

Most young people said that it is very important to tell others around you that you have Type 1 diabetes; that you should always tell your friends what the signs of a hypo and a high are and to tell them what to do in those situations. (See also 'Support from parents and families' and 'Friends and relationships'). They also said that it is a good idea if you are going out to wear a diabetes pendant or some diabetes-type of identity so the paramedic will know exactly what to do with you if you end up unconscious.

Last reviewed April 2010.

Last update April 2010.