Hyperglycaemia

Also called High blood sugar

Blood glucose too high. Usually manageable at home, and the reason to check ketones rather than just repeating the glucose test.

What it is

A blood glucose level above the target range, in somebody with or without a known diagnosis of diabetes.

Occasional high readings are part of life with diabetes and are not an emergency. Persistent highs cause thirst, tiredness, blurred vision and infections, and over years drive the complications: eye, kidney, nerve and cardiovascular damage.

The reason it has its own entry is what to do when it happens, which people are frequently not taught clearly.

**In type 1 diabetes, a high glucose is a prompt to check ketones**, not simply to give more insulin and re-test. Raised ketones mean the body is breaking down fat and heading towards diabetic ketoacidosis, which is a medical emergency.

**In type 2 diabetes, particularly in older people, very high glucose with severe dehydration** can cause hyperosmolar hyperglycaemic state, which develops over days and has a high mortality. Thirst, confusion and drowsiness in an older person with diabetes needs urgent assessment.

Common triggers are illness and infection, missed or wrong medication, steroid treatment, pump or cannula failure, stress, and eating more carbohydrate than the dose covers.

Steroids are a particularly common and predictable cause and are frequently prescribed without any plan for the glucose.

Signs you might notice

Increased thirst and a dry mouth.

Passing urine much more often, including at night.

Tiredness and weakness.

Blurred vision.

Headache.

Recurrent infections: thrush, urinary infections, skin infections, slow-healing wounds.

Weight loss, particularly in undiagnosed type 1 diabetes.

999 or urgent: vomiting, abdominal pain, deep rapid breathing, breath smelling of pear drops, drowsiness or confusion, or blood ketones above 3.0.

In an older person: confusion, drowsiness and severe dehydration with very high glucose.

New symptoms in an undiagnosed person, especially a child, need a same-day finger-prick test. See the four Ts under diabetic ketoacidosis.

How it can affect day-to-day life

A written sick day plan is the single most useful thing anybody with diabetes can have, and it should exist before it is needed.

Continuous glucose monitors have changed daily management, and understanding the trend arrow, whether glucose is rising or falling, is more useful than any single number.

Steroid courses reliably raise glucose, usually peaking in the afternoon and evening, and anybody with diabetes starting steroids should have a monitoring and adjustment plan.

Chasing every high with extra insulin causes a rollercoaster of highs and lows; adjusting the background regimen is usually the answer, and that is a conversation with the diabetes team.

Fear of hypoglycaemia leads many people to run their glucose deliberately high, and it deserves discussing openly rather than being treated as poor control.

For anybody who cannot report symptoms, thirst, drowsiness and increased wetting are the things carers should watch for.

Supporting someone well

In type 1 diabetes, check ketones whenever glucose is persistently high, and always when unwell or vomiting.

Have a written sick day plan, and never stop insulin.

Keep drinking sugar-free fluids.

Look for the cause: illness, missed doses, a failed pump cannula, steroids, or a change in eating.

Ask for a plan before starting steroids.

Do not chase every high with extra insulin; discuss the pattern with the diabetes team.

Get vomiting with high glucose seen urgently; that is not a home problem.

For older people, treat confusion and drowsiness with high glucose as an emergency.

Ask about continuous glucose monitoring, and learn to read the trend rather than the number.

Where to get help

The diabetes team's advice line, used early rather than late.

999 for vomiting, drowsiness, confusion, deep rapid breathing, or ketones above 3.0.

A GP practice the same day for a child with thirst, weight loss and passing urine frequently.

Diabetes UK helpline: 0345 123 2399.