high sugar specialist tests overview

Overview

High blood sugar (also called hyperglycemia) means there is too much glucose (a type of sugar) in your blood. Glucose comes from the food you eat and is used by your body for energy. When your body cannot control glucose properly, levels can become too high. Tests help doctors check if your blood sugar is in a healthy range or if you might have prediabetes or diabetes.

Yes, high blood sugar is common. According to the NHS, more than 5 million people in the UK are estimated to have diabetes (including undiagnosed cases). Prediabetes, where blood sugar is higher than normal but not yet diabetes, is also common.

High blood sugar can affect anyone, but it is more common in people over 40, those who are overweight, have a family history of diabetes, or are of certain ethnic backgrounds (such as South Asian, African-Caribbean, or Hispanic).

Symptoms

Common symptoms

• Feeling very thirsty
• Urinating more often than usual (especially at night)
• Feeling very tired
• Blurred vision
• Unexplained weight loss
• Slow healing of cuts or wounds
• Tingling or numbness in hands or feet

Symptoms in children

• Frequent urination (bedwetting in children who were previously dry at night)
• Increased thirst
• Weight loss despite normal or increased eating
• Irritability or mood changes

Symptoms in older adults

• Confusion or trouble thinking clearly
• Frequent infections (like urinary tract infections)
• Fatigue that gets worse over time
• Blurred vision

Causes

Main causes

• The body cannot make enough insulin (a hormone that controls blood sugar)
• The body becomes resistant to insulin, so it does not work properly
• Eating too many sugary or starchy foods can cause temporary high blood sugar

Risk factors

• Being overweight or obese
• Not getting enough physical activity
• Having a family history of diabetes
• Being over 40 years old (over 25 for South Asian people)
• Having high blood pressure or high cholesterol
• A history of gestational diabetes (diabetes during pregnancy)

When to see a doctor

See a doctor urgently if:

• If you have symptoms of very high blood sugar such as confusion, deep rapid breathing, or fruity breath
• If your blood sugar is very high and not coming down with your usual management

Book a routine appointment if:

• If you have any of the common symptoms like increased thirst, frequent urination, or fatigue
• If you are over 40 and have other risk factors
• If you have a family history of diabetes

Diagnosis

High blood sugar is diagnosed with blood tests. Your doctor will order one or more tests to check your blood sugar levels. The results help them see if your levels are in the normal range, prediabetes range, or diabetes range.

Tests that may be done

• Fasting plasma glucose test – measures your blood sugar after you have not eaten for at least 8 hours
• HbA1c test – shows your average blood sugar over the past 2-3 months
• Oral glucose tolerance test (OGTT) – checks how your body handles a sugary drink after fasting
• Random plasma glucose test – measures blood sugar at any time, regardless of when you last ate

What to expect at your appointment

For most tests, you will need to have blood drawn from a vein in your arm. For the fasting test, you will need to not eat or drink anything except water for at least 8 hours before the test. The HbA1c test does not require fasting. The OGTT takes a few hours because you drink a sugary liquid and then have blood drawn again after 2 hours. Your doctor will tell you exactly how to prepare for each test.

Treatment

If you are diagnosed with high blood sugar (prediabetes or diabetes), there are many ways to manage it. Treatment focuses on lowering your blood sugar to a healthy range and preventing complications. It often includes lifestyle changes and, if needed, medications.

Self-care at home

• Monitor your blood sugar levels as advised by your healthcare team
• Follow a balanced diet that limits simple sugars and refined carbohydrates
• Stay physically active (aim for at least 30 minutes of moderate activity most days)
• Maintain a healthy weight
• Take all medications exactly as prescribed
• Attend regular check-ups and diabetes education programs

Medical treatments

Treatment for high blood sugar may include medications that help your body use insulin better or help your pancreas release more insulin. Some people may need insulin injections. Your doctor will work with you to find the best treatment plan for your needs. They will consider your blood sugar levels, your overall health, and your personal preferences.

When is surgery considered?

Surgery is usually not a direct treatment for high blood sugar. However, for some people with obesity and type 2 diabetes, bariatric (weight loss) surgery can improve blood sugar control. This is only considered for certain individuals. Talk to your doctor if you think this might be an option for you.

Living with this condition

Living with high blood sugar means paying attention to your diet, activity, and medication. You may need to check your blood sugar regularly and adjust your meals or insulin. It can take time to get used to, but many people manage it well with support.

Lifestyle tips

• Eat regular meals and avoid skipping meals
• Choose whole grains, vegetables, lean protein, and healthy fats
• Limit sugary drinks and sweets
• Include physical activity in your daily routine (walking, swimming, biking, etc.)
• Get enough sleep and manage stress

Diet and exercise

A healthy diet and regular exercise are key to managing high blood sugar. Aim for meals that are balanced with carbohydrates, protein, and fat. Exercise helps your body use insulin more effectively. Even a 10-minute walk after meals can help lower blood sugar. Talk to your doctor before starting a new exercise plan.

Mental health and emotional wellbeing

Living with a long-term condition like high blood sugar can affect your mental health. You may feel stressed, anxious, or depressed. This is common and nothing to be ashamed of. If you are struggling, talk to your doctor or a counsellor. Support groups and online communities can also help. If you are having thoughts of harming yourself, please contact a crisis helpline immediately.

Prevention

For some people, high blood sugar (especially type 2 diabetes) can be prevented or delayed. Healthy eating, regular exercise, and maintaining a healthy weight are the most effective strategies. If you have prediabetes, these lifestyle changes can sometimes bring your blood sugar back to normal.

Screening programmes

Routine blood tests, such as the HbA1c test, can detect high blood sugar early. If you have risk factors (like being overweight or having a family history), your doctor may recommend screening every 1 to 3 years. Early detection allows for early treatment and can prevent complications.

Complications

If left untreated

• Heart disease and stroke
• Kidney disease (nephropathy)
• Nerve damage (neuropathy), causing pain or numbness in your hands and feet
• Eye problems (retinopathy) that can lead to blindness
• Foot problems, including infections and ulcers that may lead to amputation
• Increased risk of infections

Long-term outlook

With proper management and treatment, most people with high blood sugar can lead full, active lives. Controlling your blood sugar reduces the risk of complications. Your outlook depends on many factors, but staying engaged with your healthcare team and following your treatment plan gives you the best chance for a healthy future.

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