Hyperglycaemia, or a hyper, is when your blood glucose levels, also called blood sugar levels, are too high.
For many people a level above 7mmol/l before a meal and 8.5mmol/l two hours after a meal would be a hyper, but target levels can be different for everyone and should be individually agreed by you and your healthcare team.
Hypers happen because the body either can’t produce enough of the hormone insulin, or the insulin it makes doesn’t work very well.
When you eat or drink, any carbohydrates you've had are turned into glucose, a type of sugar. Insulin acts like a key to unlock the cells to let the sugar in, to give you energy. If you don’t have enough insulin, or it doesn’t work very well, sugar builds up in the blood. This can cause symptoms and can be serious if not treated.
On this page we cover:
- What causes hyperglycaemia?
- Symptoms of hyperglycaemia
- Treating and managing hyperglycaemia
- How to prevent hyperglycaemia
- Can drinking water lower blood sugar levels?
- If you regularly have high blood sugar
What causes hyperglycaemia?
There are several reasons why your blood sugar levels may be too high. Hypers can be caused by:
- missing a dose of your medication
- eating more carbohydrates than your body or medication, or both, can cope with
- being stressed
- being unwell from an infection
- accidentally over-treating a hypo
- taking steroids
- your body reacting to something you may not be aware of.
Signs and symptoms of hyperglycaemia
When your blood sugar levels are slightly higher than normal, you will not usually have any symptoms. But as they rise, symptoms may include:
- going for a wee a lot, especially at night
- being really thirsty
- feeling more tired than usual
- thrush or other recurring bladder and skin infections
- headaches
- blurred eyesight
- losing weight without trying to
- feeling sick.
Symptoms of hyperglycaemia may build up slowly over time as your sugar levels rise. This means you may not notice them until your blood glucose is very high.
If you have these symptoms, you should take action straight away to reduce your blood sugar levels. See below:
Treating and managing hyperglycaemia
If your blood sugar level is slightly high for a short time, emergency treatment is not needed. But if it continues to rise you may need to act fast to avoid developing diabetic ketoacidosis (DKA) or hyperosmolar hyperglycaemic state (HHS).
If your blood sugar level is high, usually above 13mmol/l or 14mmol/l, you should check for ketones. Everyone with type 1 diabetes will need a blood ketone meter which you should get for free from the NHS. If you’re not sure if you should check for ketones, it’s really important that you check with your healthcare team. If you have type 2 or another type of diabetes you might need to check your urine or blood for ketones if you take diabetes medication such as insulin or an SGLT2 inhibitor.
If ketones are present, it is likely that you don’t have enough insulin in your body. This means you may need to increase your dose of insulin or give yourself an extra dose. Talk to your diabetes team about how to do this if you are unsure.
You should also try to drink plenty of water and other sugar-free fluids to prevent dehydration. And if you’re feeling unwell, especially if you are vomiting, you should follow any ‘sick day rules’ you discussed with your diabetes team and contact them for advice.
“For me hypos are usually very easily treated. But I find hypers on the other hand, are very resistant to responding to insulin and often take hours and multiple injections to come down and I have to monitor my levels quite closely.” A forum user.
If your blood sugar levels are regularly above 10mmol/l you should contact your diabetes team or GP. They will review your treatment and provide you with advice on how to get your blood sugar levels back within your target range. This advice may include increasing your medication.
Can drinking a lot of water lower your blood sugar levels?
Drinking water regularly can help to keep your blood sugars lower. But when your blood sugar has been high for a while, drinking a lot of water won’t be enough to bring your blood sugars down. Although feeling very thirsty can be a symptom of a hyper, drinking a lot of water will only quench the thirst and help to reduce your risk of dehydration.
It’s important that you take your diabetes medication to bring your blood sugar levels down. If you have consistently high blood sugar levels, speak to your diabetes team.
How to prevent hyperglycaemia
Checking your blood sugar levels regularly can help you know when your blood sugar levels are high. But there are some steps you can take to either prevent a hyper from happening or to bring down your blood sugar levels.
Here are some of the things that can help:
- Take your diabetes medications, including your regular insulin dose, as you have discussed with your diabetes team.
- If you’re ill, follow any sick-day rules you’ve discussed with your diabetes team and speak to your doctor, especially if you aren’t eating.
- Think about your carbohydrate portions and how they may be affecting your blood sugar levels after eating. Carb counting is one of the ways you can manage this.
- Continuous Glucose Monitors (CGM) have alarms that alert you when your blood sugar is high or low so you can take appropriate action sooner. CGM can also help with diabetes management as you have more information about when you're high or low.
- Choosing foods lower on the Glycaemic Index ( GI) which tells us whether a food raises blood glucose levels slowly, moderately or quickly can be useful for managing blood glucose levels. These (lower GI) foods include most fruit and vegetables, unsweetened milk, nuts, pulses and some wholegrain cereals.
- Increase the fibre in your diet. This can help slow down how quickly carbohydrates are digested, which can help limit the rise in your blood sugar levels after eating.
- Get support to manage your weight. This may be maintaining your current weight or taking steps to lose weight. Weight loss can help make insulin work more effectively.
- Keep physically active as this can help keep blood sugars lower.
It is also important to look after your emotional wellbeing, get good quality sleep and get support to manage stress. Stress can cause hormones to be released, which can keep your blood sugar levels high.
If your blood sugar levels continue to be high, or you’re unsure of what to do, speak to your diabetes team for further support.
If you regularly have high blood sugar levels
Regularly having high blood sugar levels is not good for your body. This is because in the long-term it can increase your risk of developing diabetes complications, such as neuropathy and retinopathy.
If you notice that your blood sugar levels are often higher than the target range discussed with your diabetes team, you should speak to them to discuss the options.
They will review your treatment and provide you with advice on how to get your blood sugar levels back within your target range. This may include increasing your medication dose or changing or adding another medication.
In the video below, Lynsey about feeling anxious after getting a high blood sugar level reading. If you’re finding it hard to deal with similar feelings, we’ve got information on emotional health that you may find helpful.
Getting support
If you are concerned about any aspect of managing diabetes, you can always call our helpline for support on 0345 123 2399. Alternatively, you can head over to our forum where there are many people willing to offer support and share their experiences of diabetes.
