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High blood sugar

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 3 minutes read

High blood sugar is called hyperglycaemia. This is when the blood sugar level goes above the normal range. It mainly affects people with diabetes, or is used to diagnose diabetes.

Normal blood sugar (glucose) levels are between 4 and 7 mmol/l before eating a meal, or above 8.5 mmol/l 2 hours after eating. It will go up after eating, and you produce insulin to reduce it so glucose can be stored and released gradually for a constant source of energy. Diabetics do not produce enough insulin to counteract this, therefore they require medication and diet restrictions to avoid high blood glucose levels.

If it reaches very high levels, such as above 15 mmol/l, or stays high for a sustained period, this can cause health problems, and if extremely high, in the mid-20's this can lead to an emergency that requires urgent hospital attention.

What causes high blood sugar?

High blood sugar can be caused by not controlling the amount of sugar you eat, lack of exercise, increased stress, not taking your diabetic medication or insulin correctly or on time, or taking certain medications such as steroids in the long term.

What are the symptoms?

Symptoms of high blood sugar levels can develop slowly over time and in some cases, there are no symptoms until levels are very high. Symptoms include increased thirst, needing to urinate more frequently or passing lots of urine each time, tiredness, blurred vision, unintentional weight loss, recurrent urine infections, abdominal pain, nausea and vomiting.

You are at risk of very high blood sugar levels if you are diabetic, and if you become unwell with, for example, a chest infection, you are dehydrated, you have missed a dose of diabetic medication or you have eaten lots of sugar or carbohydrates. You are at even greater risk if you usually take insulin.

Untreated high blood sugar over the long term can lead to cardiovascular disease, nerve damage, kidney damage, kidney failure and even damage to the blood vessels of the eyes, which can lead to blindness.

How can I prevent high blood sugar?

To prevent high blood sugar, you should try and control the amount of sugar that you consume, perform at least 20 minutes of exercise daily and have a nutritious healthy balanced diet. If you are overweight or obese, you should try losing weight by calorie control, exercise, or seeking a weight management programme via your doctor.

When should I see my doctor?

If you constantly get the symptoms described above then you should speak to your doctor, who will take a history and ask you for a urine and blood test.

If your blood sugar level is raised on two occasions, or raised on one occasion with symptoms then they will likely start you on medication. You will need regular blood tests to ensure your levels are coming down and that your kidneys are in good health. Your doctor may refer you to a specialist diabetic team or to specialist diabetic programme to help improve your sugar levels.

If you are diagnosed as a diabetic, you will learn about how to regulate sugar levels by eating healthy, low-sugar meals regularly and taking your diabetic medication. If you need insulin, you will be taught to match activity levels, foods and insulin dose, using a blood glucose monitoring machine. You may wish to buy one if diabetic but not on insulin.

If blood glucose levels go high, you will be taught how to counteract this, and you may be provided with urine strips to check ketone levels, too. You will be told under what conditions you should seek urgent medical attention.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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