High Blood Sugar Hyperglycaemia

Overview

High blood sugar, also called hyperglycaemia (say: hy-per-gly-SEE-mee-ah), means there is more sugar in your blood than is healthy. Your body gets sugar from the food you eat, and a hormone called insulin acts like a key that lets sugar move from your blood into your cells for energy. If your body does not make enough insulin, or the insulin does not work well, sugar builds up in the blood instead. This is very common in people with diabetes, but it can also happen during illness, stress, or with some medicines. High blood sugar is usually something you can spot early and bring back down with the right care.

Yes, it is very common. Most people living with diabetes have high blood sugar at some point, and many have mild highs every week. It is one of the most frequent reasons people with diabetes contact their doctor, nurse, or pharmacist.

It mainly affects people with type 1 or type 2 diabetes, and people who had diabetes during pregnancy (gestational diabetes). It can also affect people taking steroid medicines, people who are seriously unwell or stressed, and people whose diabetes has not yet been diagnosed. Children, teenagers, and older adults can all be affected, though the signs can look quite different at different ages.

Symptoms

Common symptoms

• Feeling very thirsty, even after drinking
• Peeing more often than usual, especially getting up at night to pee
• Tiredness, low energy, or feeling drained
• Blurred or fuzzy vision
• Dry mouth
• Headaches
• Cuts, grazes, or sores that heal more slowly than usual
• Getting infections more often, such as thrush, urine infections, or skin infections
• Unexplained weight loss (more common in type 1 diabetes)
• Feeling hungry more than usual
• Needing to pee a lot can also make you feel dizzy or lightheaded from dehydration

Symptoms in children

• Being much thirstier than usual and drinking a lot
• Wetting the bed or having accidents after being dry for a while
• Peeing very often, including at night
• Being more tired, quiet, or grumpy than usual
• Tummy pain or feeling sick
• Losing weight or looking thinner without trying
• Poor concentration at school
• In children with type 1 diabetes, these signs can come on quickly — within days — and need medical advice fast

Symptoms in older adults

• Signs can be quieter and easier to miss — thirst may not be strong, even when dehydrated
• Confusion, muddled thinking, or being more forgetful than usual
• Feeling very tired, weak, or unsteady on your feet
• Falls, or finding it harder to get around
• Losing control of your bladder, or needing to pee very urgently
• Dry mouth, dry skin, or sunken eyes from dehydration
• Feeling generally 'not yourself' — a change in behaviour can be the main clue

Causes

Main causes

• Not enough insulin being made or released by the body
• Insulin not working well — this is called insulin resistance, and it is common in type 2 diabetes
• Missing, delaying, or being unsure about diabetes medicines or insulin doses
• Illness or infection — the body releases stress hormones that push blood sugar up
• Physical or emotional stress, including pain, surgery, or bereavement
• Eating more carbohydrate (sugary and starchy foods and drinks) than usual
• Being less active than usual, for example during recovery or a holiday
• Steroid medicines and some other prescription medicines
• Problems with how insulin is given — for example, a blocked or bent cannula, an expired insulin, or injecting into a lumpy area
• Hormone changes, such as during puberty or the menstrual cycle
• The 'dawn' effect — natural hormone changes in the early morning that raise blood sugar

Risk factors

• Having type 1 or type 2 diabetes
• Having had gestational diabetes during a pregnancy
• Being overweight, especially around the waist
• A family history of type 2 diabetes
• Taking steroid medicines or some other prescription medicines
• Being unwell, recovering from surgery, or under a lot of stress
• Older age, especially when combined with dehydration or illness
• Long gaps between diabetes check-ups, or not having a clear sick-day plan

When to see a doctor

See a doctor urgently if:

• Blood sugar is much higher than usual and keeps rising despite following your plan
• You have symptoms of dehydration — very dry mouth, little urine, dizziness on standing
• You are vomiting or have a fever and cannot keep fluids down
• You are checking ketones and they are positive (ask your team what to do, and when to go to hospital)
• You notice any confusion, unusual drowsiness, or fast deep breathing — call your local emergency number right away
• You are pregnant and your blood sugar readings are high
• You cannot keep your diabetes medicines down because of vomiting

Book a routine appointment if:

• Your blood sugar readings are often higher than your target range
• Symptoms like thirst, tiredness, and peeing a lot keep coming back
• You have repeated infections, slow-healing wounds, or thrush
• You have lost weight without trying
• You are unsure how to adjust your diabetes plan when you are ill
• You feel you need a review of your diabetes medicines or a refresher on injecting or monitoring

Diagnosis

If you already have diabetes, high blood sugar is usually checked with a finger-prick blood glucose meter, or a sensor that reads your glucose continuously. If you do not yet have a diabetes diagnosis, your doctor will arrange blood tests. The main test is often done in the morning before eating, or as an average measure over the last few months. Your doctor will also ask about your symptoms, your medicines, and any recent illness, and may check your blood pressure and weight.

Tests that may be done

• Finger-prick blood glucose check or a continuous glucose sensor reading
• A blood test called HbA1c, which shows your average blood sugar over the last two to three months
• A fasting blood glucose test (taken before you eat in the morning)
• A ketone check — a small blood or urine test that looks for harmful acids
• Blood tests to check salt levels and kidney function if you are dehydrated or unwell
• A urine test to look for infection or sugar in the urine
• Other tests if needed, such as a check for infection or an ECG if you feel unwell

What to expect at your appointment

Most of this is quick and simple. A finger-prick result appears in seconds. Blood tests are usually taken from a vein in your arm and results come back within days. Your clinician will talk you through what your numbers mean, what your personal target range is, and what to do next. Bring your meter or sensor app, your medicine list, and any notes about your readings so you can go through them together.

Treatment

The aim is to bring your blood sugar back into your target range gently and safely, and to treat whatever caused the rise. For mild highs, simple steps at home — checking more often, drinking water, and following your own care plan — often do the job. If your readings keep running high, your diabetes team may adjust your diabetes medicines, your eating plan, or the way you monitor. If you become very dehydrated or unwell, treatment in hospital with fluids and closely supervised diabetes medicines may be needed. There is no single 'right' approach — your plan is tailored to you.

Self-care at home

• Check your blood sugar more often than usual while things are unsettled, and write the readings down
• Drink plenty of water or sugar-free drinks to stay hydrated — sip regularly if you feel sick
• Follow the 'sick-day plan' your diabetes team has given you, if you have one; ask for one if you don't
• Keep taking your diabetes medicines as usual unless your healthcare team tells you otherwise
• Check for ketones if your team has advised this, and know what to do with the result
• Rest, and avoid intense exercise while your readings are high, as hard exercise can push sugar up further
• Avoid sugary drinks, sweets, and fruit juice while your sugar is high, unless you are treating a low
• Have a plan for eating when you feel unwell — small, light meals or snacks can help
• Ask your pharmacist before taking cold, flu, or pain remedies, as some can affect blood sugar

Medical treatments

Treatment is about restoring balance. Your care team may review and adjust your diabetes medicines, change how your treatment is given, or change the timing of what you take. If you take insulin, they can help you fine-tune your routine and injection technique. If you are dehydrated, you may be given fluids. If an infection or illness is the trigger, that is treated too. In more serious cases, people are cared for in hospital so their fluids, salt levels, and blood sugar can be monitored closely and corrected safely. Your team will also help you spot the early warning signs so you can act sooner next time.

When is surgery considered?

Surgery is not a treatment for high blood sugar. However, if you need an operation for another reason, your diabetes will be carefully planned for beforehand, because illness and surgery can raise blood sugar. Tell your surgical and anaesthetic team about your diabetes and any medicines you take well in advance, and ask for a pre-operative review.

Living with this condition

Living with high blood sugar, or with diabetes more generally, means learning your own patterns. Many people find that a simple routine helps: checking at similar times, noting readings along with meals, activity, and stress, and keeping water nearby. It is normal for readings to wander — a single high day is information, not failure. Over time you become the expert on your own body, and your care team is there to fine-tune things with you.

Lifestyle tips

• Eat regular meals and try to keep the amount of carbohydrate fairly steady from day to day
• Choose water or sugar-free drinks as your everyday drink
• Build gentle activity into your day — even short walks help your body use sugar better
• Aim for a healthy sleep routine, as poor sleep can raise blood sugar
• Plan ahead for illness: keep a sick-day kit with test strips, ketone checks if advised, and sugar-free drinks
• Limit alcohol, and never drink on an empty stomach if you take diabetes medicines that can cause lows
• Keep up with your routine diabetes reviews, eye checks, and foot checks
• Ask for help with stopping smoking — it lowers your risk of heart and circulation problems

Diet and exercise

Food and movement are two of the most powerful tools you have. You do not need a perfect diet — steady, realistic changes work best. Eating regular meals, choosing more vegetables, pulses, whole grains, and lean proteins, and cutting back on sugary drinks can make a real difference to your readings. Activity helps your muscles take up sugar from your blood, so even 10 to 15 minutes of walking after a meal can help. If you take medicines that can cause low blood sugar, check with your team before starting a new or harder exercise routine, as your plan may need adjusting.

Mental health and emotional wellbeing

High blood sugar can take an emotional toll. Many people feel frustrated, guilty, or anxious about their numbers, and 'diabetes burnout' — feeling tired of managing it all — is very common and completely understandable. Feeling low or worried can also raise blood sugar, which can feel like a loop. Be gentle with yourself. Talking to your diabetes team, a counsellor, or other people with diabetes often helps a lot. If you are feeling overwhelmed, hopeless, or having thoughts of harming yourself, please reach out for crisis support straight away — contact your local crisis line, your doctor, or your local emergency number. You do not have to cope alone.

Prevention

You cannot always prevent high blood sugar, especially with type 1 diabetes where it is part of daily life. But you can greatly reduce how often and how badly it happens. Learning your triggers, having a clear sick-day plan, checking more often when you are unwell, and keeping your medicines and injection technique in good shape all help. If you are at risk of type 2 diabetes, healthy eating, regular activity, and weight loss can delay or even prevent it — ask your doctor about your risk.

Screening programmes

If you have diabetes, regular reviews — including an HbA1c blood test, blood pressure, kidney, eye, and foot checks — help catch rising blood sugar early. If you do not have diabetes but have risk factors such as being over 40, having a family history, or being overweight, ask your GP or pharmacist about a diabetes risk check. In the UK, the NHS Health Check includes this, and free checks are often available at local pharmacies.

Complications

If left untreated

• Diabetic ketoacidosis (DKA) — a serious build-up of harmful acids in the blood, most common in type 1 diabetes, which needs emergency hospital care
• Hyperosmolar hyperglycaemic state (HHS) — severe dehydration and very high blood sugar, more common in older people with type 2 diabetes
• Long-term damage to the eyes, which can affect sight
• Kidney damage over time
• Nerve damage, causing numbness, tingling, or pain, especially in the feet
• Heart disease and stroke
• Poor healing and foot ulcers, which can become serious
• More frequent infections, including urine and skin infections
• Problems with sexual function
• Gum and teeth problems

Long-term outlook

The outlook is genuinely positive. Many people live full, active lives with diabetes and keep their blood sugar in a healthy range most of the time. High readings are a signal to adjust, not a sign that you have failed. With regular checks, a plan you understand, and a team you can call, most highs can be spotted early and sorted out quickly. Every small step you take — a walk, a glass of water, a check you would have skipped — counts in your favour.

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