Hyperglycaemia is high blood glucose. It mainly affects people with diabetes and can become serious if it is not recognised and treated.
Blood glucose rises when there is not enough effective insulin to move glucose from the blood into cells. A short rise may happen after food or illness, but persistent or very high glucose can damage the body and may lead to emergencies such as diabetic ketoacidosis.
Blood Glucose Levels
Blood glucose targets vary depending on the person, the type of diabetes, age, treatment, pregnancy status, and advice from the diabetes care team.
The NHS gives general guide levels for high blood sugar in diabetes, including:
- HbA1c of 48 mmol/mol or over, also written as 6.5%.
- Fasting glucose over 7 mmol/L.
- Home testing over 7 mmol/L on waking or before eating.
- Home testing over 11 mmol/L at least 90 minutes after eating.
These are guide levels, not personal targets. People with diabetes should follow the plan agreed with their care team.
Symptoms
Symptoms usually develop gradually and may include:
- Feeling very thirsty.
- Urinating a lot.
- Feeling weak or tired.
- Blurred vision.
- Losing weight.
- Recurrent infections, depending on the situation.
Some people have high glucose without obvious symptoms, especially if the rise is mild or gradual.
Causes
Common causes in people with diabetes include:
- Being unwell or having an infection.
- Stress.
- Eating more sugary or starchy food than usual.
- Being less active than usual.
- Missing doses of diabetes medicine.
- Diabetes medicine not working well enough.
- Taking medicines such as steroids.
- Recent surgery or another physical stress.
Management
Management depends on the person's diabetes plan and how high the glucose level is. General measures may include checking blood glucose, taking prescribed diabetes medicine as advised, following sick-day rules, drinking enough fluids, avoiding excess sugary or starchy food, and contacting the diabetes care team if levels remain high.
People should not skip or change prescribed diabetes medicine unless advised by a doctor or diabetes care team.
Complications
High glucose can cause serious problems if it stays high for a long time or becomes very high. Possible complications include:
- Peripheral neuropathy.
- Diabetic retinopathy.
- Heart disease and stroke.
- Kidney disease.
- Diabetic ketoacidosis, especially in people with type 1 diabetes but possible in other situations.
A high ketone level in blood or urine can be a warning sign of diabetic ketoacidosis. NHS advice is to seek urgent help if high blood sugar is accompanied by symptoms such as vomiting, stomach pain, fast breathing, drowsiness, confusion, fruity-smelling breath, or high ketones.
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