Blood glucose levels are measured in units called mmol/L (pronounced milli-moles-per-litre). The ideal ranges are:
- Before meals: 4-7 mmol/L
- Two hours after meals: 8-9 mmol/L
- At bedtime: 6-10 mmol/L
You may need to consult your doctor and change your treatment plan if:
- Blood glucose is consistently lower than 4 mmol/L or higher than 10 mmol/L before meals
- Blood glucose is consistently lower than 6 mmol/L or higher than 12 mmol/L at bedtime
- Blood glucose goals may be modified for children and others who are at greater risk of hypoglycaemia
In the US, blood glucose levels are measured in mg/dl (milligrams per deciliter). That’s why you’ll occasionally read about blood glucose readings that seem very high, like 140 or 220. To convert the American scores back to mmol/L, just divide the number by 18.
How often should I be checking my blood glucose levels?
Checking your blood glucose levels and keeping a record of the levels is an important part of taking care of your type 1 diabetes. This allows you to identify the patterns of high or low blood glucose levels. The information will also help you and your doctor or diabetes team to balance food, exercise and insulin doses.
Ideally you should aim to do at least four blood glucose levels checks a day, although some people do many more. To get the most out of monitoring, your healthcare team may advise you to check your blood glucose levels before and then two to three hours after food. It’s also a good idea to monitor before, during and after exercise.
If your blood glucose level is high, like when you’re feeling unwell, you should also monitor for ketones. You can do this using a blood glucose meter that also measures for ketones or by checking your urine. Ketones in the blood or urine can also indicate that your insulin levels are too low. If this is the case, you’ll need to take additional insulin as a matter of urgency so your body can use glucose for energy rather than fat.