Is my background insulin correct?

This graph below shows an approximate insulin profile throughout a 24 hour period for someone taking a combination of once or twice a day long-acting insulin and short-acting insulin with each meal. As you can see the only insulin working overnight is the long-acting insulin.

Overnight Check

A good way to check if your basal insulin dose is correct is to monitor your blood glucose levels before bed (ideally 4 hours or more after food), and when you wake up. If your bed-time level is between 6 – 8 mmol/L and your waking glucose levels are within the target range of 5 – 7 mmol/L, your basal insulin dose is likely to be correct.

During the night, it’s not unusual for your blood glucose to drop between 2 – 3 mmol/L – it shouldn’t drop any more than this. If your reading before you go to bed is too high then it suggests that your evening meal ratio needs reviewing so that you are within your target range before going to sleep.

Adjusting your basal insulin

If there is a significant rise in blood glucose overnight, it may suggest your basal insulin dose is too low and needs to be increased.

If there is a significant drop in blood glucose overnight, it may suggest your basal insulin dose is too high and needs to be reduced

It’s important not to make any immediate changes based on one reading, instead monitor this closely over a few days to see whether there is a pattern to your blood glucose levels.

Day Time Check

Another way to check your basal insulin is to have a carbohydrate and bolus insulin-free lunch

If you miss your lunch or have a carbohydrate free lunch, the only insulin working over the afternoon is the long acting insulin so it will be responsible for changes in blood glucose.

If your blood glucose 2-4 hours after eating (or your pre-evening meal blood glucose level) is similar to your pre-lunch readings (and ideally both within the target range), this would indicate that you’re taking the right amount of basal insulin. Ideally, repeat this on 3 consecutive days. You can download a diary to keep track of your carbohydrate, insulin doses and blood glucose levels by clicking here.

Adjusting your basal insulin

If blood glucose rises over the afternoon in this scenario, your basal dose may need to increase. If blood glucose falls, your basal dose may need to reduce.

Your diabetes care team will be able to advise you on adjusting your basal insulin. You should only make minor adjustments (for example a 10% increase or decrease in the insulin dose) and monitor the effects, and then adjust again if needed.

Have a look at the example below of Denis and his blood glucose level readings. He takes his basal insulin once a day in the evening. How do you think his basal insulin should be adjusted? Does he need to take more or less insulin?

Date	Before Breakfast	Before Bed
16/7	10.3	5.1
17/7	11.6	6.5
18/7	9.9	8.4
19/7	10.5	5.0
20/7	12.2	6.9