As a ‘rule of thumb’, most people require around 50% of their insulin as background and 50% as quick- acting (with meals). If your background insulin dose comprises a much bigger proportion of your total dose, it may be too high. This is important as excessive background insulin can drive your appetite (weight gain) and also leave you open to hypos. In a quarter of people, once daily background insulin starts to wear off much earlier than 24 hours.
How can I tell if my background insulin dose is correct?
The best way to test this is by occasionally having carbohydrate free meals (or fasting), which means you do not have to take any quick- acting insulin at that time point. In the example above, the patient has taken a ‘carb free’ breakfast. The black line shows what should happen if the background insulin is ‘doing its job’ – the glucose more or less remains steady. The pink line shows what would happen if someone has too much background on board – the glucose levels fall into the hypo range. The white line shows what would happen if the background insulin dose is too low – the glucose level rise over the morning. You can also perform carb free (or fasting) at lunch and tea time to see how effective the background coverage is across those periods. It is best not to do more than one in a single day!
What changes can be made?
- If glucose is falling after carb free meals (or fasting) then this suggests a decrease in background insulin.
- If glucose is rising after carb free meals (or fasting) then this suggests an increase in background insulin.
- Splitting background insulin (taken approximately 12 hours apart) can have significant advantages:
−− More consistent profile (less variable glucose levels).
−− Doesn’t run out towards the end of 24 hours.
−− Can adjust the morning or evening dose in response to exercise.
- The main disadvantage of splitting is that it can be difficult to find convenient times to administer the insulin (e.g. 8 am and 8 pm, 10 am and 10 pm, 12 am and pm 12m).