Go to page content

Using glucose sensor between meals

The glucose sensor graph provides a good idea of the way blood sugar behaves between meals. However, you should be careful with using correction doses

The glucose sensor is a good tool for finding out the effect of different meals as well as the effect on blood sugar of the mealtime insulin dose and the timing of it.

When it comes to glucose levels between meals and reactions to them, it is especially important to take into account the direction of the trend arrow and the time from the previous injection, i.e. how much of the previous rapid-acting insulin dose remains in your system.

For most people, the duration of action of rapid-acting insulin is 3–5 hours. Usually, the action of the insulin is strongest within 2 hours of the injection. This is why, as a rule, the minimum recommended interval between correction doses of rapid-acting insulin is 2 hours, even if the trend arrow indicates an increase in blood sugar. You should monitor changes in your blood sugar for the next 1–2 hours before taking an additional dose of insulin.

A common cause of high blood sugar after a meal is taking rapid-acting insulin right before or after the meal, resulting in a delayed effect.

If you underestimated the amount of carbs in your meal and, 2 hours after the meal, the glucose level is:

  • Over 14 mmol/l with the trend arrow pointing up ↑ or ↗, you can take half of your normal correction dose and check the reading again after 1 hour.

  • 10–14 mmol/l with the trend arrow pointing up ↑, you can consider taking half of your normal correction dose based on previous experience.

  • Over 10 mmol/l with the trend arrow pointing down ↓ or ↘, do not take a correction dose but check the reading after 30 minutes and again after 1 hour. In this case, your meal included a lot of fast-acting carbs or the effect of the rapid-acting insulin was delayed.

Insulin pumps and some blood glucose meters include a dose calculator, which takes into account the residual amount of insulin remaining from the previous rapid-acting insulin dose. This helps avoid overcorrection.

Updated 30.9.2023