Hyperglycemia is the medical term describing an abnormally high blood glucose (blood sugar) level. Blood sugar is measured in a sample of blood taken from a vein or from a small finger stick sample of blood. It can be measured in a laboratory either alone or with other blood tests, or it can be measured using a handheld glucometer, a small device that allows frequent monitoring of blood glucose levels without the need for a doctor’s office or laboratory.
Hyperglycemia or high blood sugar is a hallmark sign of diabetes (both type 1 diabetes and type 2 diabetes) and prediabetes. Normal ranges for blood glucose measurements can vary slightly among different laboratories, but in general a fasting (early a.m. before breakfast) glucose level is considered normal if it is between 70-100 mg/dL. Glucose levels may rise slightly above this range following a meal. Random blood glucose measurements are usually lower than 125 mg/dL.
Symptoms of hyperglycaemia
Symptoms of hyperglycaemia in people with diabetes tend to develop slowly over a few days or weeks.
In some cases, there may be no symptoms until the blood sugar level is very high.
Symptoms of hyperglycaemia include:
- increased thirst and a dry mouth
- needing to pee frequently
- blurred vision
- unintentional weight loss
- recurrent infections, such as thrush, bladder infections (cystitis) and skin infections
- tummy pain
- feeling or being sick
- breath that smells fruity
Symptoms of hyperglycaemia can also be caused by undiagnosed diabetes, so see a GP if this applies to you. You can have a test to check for the condition.
What should my blood sugar level be?
When you’re first diagnosed with diabetes, your diabetes care team will usually tell you what your blood sugar level is and what you should aim to get it down to.
You may be advised to use a testing device to monitor your blood sugar level regularly at home.
Or you may have an appointment with a nurse or doctor every few months to see what your average blood sugar level is. This is known as your HbA1c level.
Target blood sugar levels differ for everyone, but generally speaking:
- if you monitor yourself at home with a self-testing kit – a normal target is 4 to 7mmol/l before eating and under 8.5 to 9mmol/l 2 hours after a meal
- if your HbA1c level is tested every few months – a normal HbA1c target is below 48mmol/mol (or 6.5% on the older measurement scale)
What causes high blood sugar?
A variety of things can trigger an increase in blood sugar level in people with diabetes, including:
- an illness, such as a cold
- eating too much, such as snacking between meals
- a lack of exercise
- missing a dose of your diabetes medicine or taking an incorrect dose
- overtreating an episode of low blood sugar (hypoglycaemia)
- taking certain medicines, such as steroids
Occasional episodes of hyperglycaemia can also occur in children and young adults during growth spurts.
If you have been diagnosed with diabetes and have symptoms of hyperglycaemia, follow the advice your care team has given you to reduce your blood sugar level.
If you’re not sure what to do, contact a GP or your care team.
You may be advised to:
- change your diet – for example, you may be advised to avoid foods that cause your blood sugar levels to rise, such as cakes or sugary drinks
- drink plenty of sugar-free fluids – this can help if you’re dehydrated
- exercise more often – gentle, regular exercise such as walking can often lower your blood sugar level, particularly if it helps you lose weight
- if you use insulin, adjust your dose – your care team can give you specific advice about how to do this
You may also be advised to monitor your blood sugar level more closely, or test your blood or urine for substances called ketones (associated with diabetic ketoacidosis).
Until your blood sugar level is back under control, watch out for additional symptoms that could be a sign of a more serious condition.
Keeping your blood sugar in a healthy range can help prevent many diabetes-related complications. Long-term complications of untreated hyperglycemia can include:
- Cardiovascular disease
- Nerve damage (neuropathy)
- Kidney damage (diabetic nephropathy) or kidney failure
- Damage to the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness
- Clouding of the normally clear lens of your eye (cataract)
- Feet problems caused by damaged nerves or poor blood flow that can lead to serious skin infections, ulcerations, and in some severe cases, amputation
- Bone and joint problems
- Teeth and gum infections
If blood sugar rises high enough or for a prolonged period of time, it can lead to two serious conditions.
- Diabetic ketoacidosis. Diabetic ketoacidosis develops when you don’t have enough insulin in your body. When this happens, sugar (glucose) can’t enter your cells for energy. Your blood sugar level rises, and your body begins to break down fat for energy.This process produces toxic acids known as ketones. Excess ketones accumulate in the blood and eventually “spill over” into the urine. Left untreated, diabetic ketoacidosis can lead to a diabetic coma and be life-threatening.
- Hyperglycemic hyperosmolar state. This condition occurs when people produce insulin, but it doesn’t work properly. Blood glucose levels may become very high — greater than 1,000 mg/dL (55.6 mmol/L). Because insulin is present but not working properly, the body can’t use either glucose or fat for energy.Glucose is then spilled into the urine, causing increased urination. Left untreated, diabetic hyperglycemic hyperosmolar state can lead to life-threatening dehydration and coma. Prompt medical care is essential.
The following suggestions can help keep your blood sugar within your target range:
- Follow your diabetes meal plan. If you take insulin or oral diabetes medication, it’s important that you be consistent about the amount and timing of your meals and snacks. The food you eat must be in balance with the insulin working in your body.
- Monitor your blood sugar. Depending on your treatment plan, you may check and record your blood sugar level several times a week or several times a day. Careful monitoring is the only way to make sure that your blood sugar level remains within your target range. Note when your glucose readings are above or below your goal range.
- Take your medication as prescribed by your doctor.
- Adjust your medication if you change your physical activity. The adjustment depends on the blood sugar test results and on the type and length of the activity.
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