Your diabetes is well controlled when your blood glucose levels are in the normal range between 3.5 – 8mmol/L.
When your blood glucose levels are high (over 8mmol/L before meals, over 10mmol/L after meals or HbA1c over 7%):
- You may not experience symptoms until blood glucose levels are persistently above 15mmol/L. However, even levels above 8mmol/L can cause damage silently.
- An occasional high blood glucose level may occur and this is not usually a problem. Your risk of developing complications depends on your average blood glucose level, as shown by your HbA1c level.
Blood glucose levels above 15mmol/L (hyperglycaemia) may cause the following symptoms:
- Extreme thirst
- Tiredness
- Passing large amounts of urine
- Blurred vision
If high blood glucose levels are ongoing, you may also have weight loss and persistent infections, e.g. thrush (rash, itching). Sometimes people do not have symptoms even when the blood glucose level is higher than normal.
What causes high blood glucose levels?
Blood glucose levels may rise during illness, infection, stress, inactivity, weight gain, cortisone treatment or if a large amount of food or refined sugar is consumed. During stress and illness, increased levels of the hormones adrenaline and cortisol are produced, which raise the level of glucose in your blood. Extra insulin will counteract this rise, but with diabetes the pancreas is unable to produce extra insulin on demand.
For some people, the pancreas produces less insulin over time, so blood glucose levels may not be controlled with diet and exercise alone. The natural progression in most people with type 2 diabetes is for tablets to be needed after a few years, and many will also need insulin eventually.
If blood glucose levels remain above 8mmol/L over many years, damage may occur to your body’s blood vessels and organs, in particular your heart, nerves, eyes, kidneys and feet.
Tips for lowering high blood glucose levels
- Check your blood glucose levels frequently – up to four times per day. Check before and 2 hours after meals to identify problem times. Record them in your meter or diary to discuss with your health professional.
- Be more physically active. Exercise makes your insulin work more effectively and helps with weight loss. Even a small amount of weight loss will improve your blood glucose levels.
- Check your eating habits and consider if there is room for improvement.
- Keeping a record of your food intake over 2 to 3 days can help you to identify changes that would improve your blood glucose.
- If stress is a problem, try to reduce stress by taking a walk, talking to a friend or counsellor, or try some time-out or meditation for relaxation. Consider what is causing you stress and ways you can change what is happening around you, or how you think and feel about it.
- Speak to your doctor about adding or increasing your medication. Take all your prescribed medication for it to be effective. Don’t change your dose or stop taking tablets without discussing this with your doctor.
If your blood glucose levels are very high (>15) or you are unwell
- Check your blood glucose levels more frequently – at least 4 times per day. Record them in your meter or diary to discuss with your health professional.
- Drink plenty of sugar-free fluids, such as water, mineral water, diet soft drinks.Dehydration can develop quickly, especially if you have diarrhoea or vomiting.
- If you take diabetes medication, continue your usual dose, even if you are not eating. Your dose may need to be increased or you may need a change in type of medication or insulin.
- If you are not currently taking medication, you will most likely need to start tablets or possibly insulin, at least until you are well again.
- Continue eating if possible. Light meals may be preferred, such as toast, dry biscuits or fruit. If you cannot eat and your blood glucose is under 15 mmol/L, sip juice instead.
- Rest until you are feeling well.
Contact your doctor if:
- Your blood glucose levels remain higher than 10mmol/L for a week, or more than
15mmol/L for 24 hours
- You become unwell or drowsy
- You are vomiting or have diarrhoea for more than 24 hours
- You are unable to keep fluids down for more than 12 hours.