21 October 2020

Figuring out insulin adjustments

by Cas Eliëns

I am not a doctor. The advice below is based on my own experience with diabetes. You should not use this to replace the advice of an endocrinologist. Always be critical of advice you read online, especially when it relates to your health.


I am active in an online diabetes support community. In there, people sometimes ask questions about why their blood glucose is consistently too high or too low. This advice could help in answering this question.

I have experience with insulin pump treatments with Novorapid (Novolog) and Fiasp, as well as manual injections with a separate bolus (Novorapid, Fiasp) and basal (Lantus, Tresiba) insulins.

If you think your nighttime basal rate (especially when using a pump) might need to be adjusted. Consider checking out my nighttime basal test

Always consult a doctor before changing your insulin dosages

Getting data

I believe that the most important factor in figuring out why your blood glucose level isn’t doing what you want is testing, and doing so often. To form a useful picture of your glucose during the day, I recommend testing at least as follows:

This should give you about eight data points per day.

Why is this useful?

Testing before and after a meal helps show a picture of how the meal affects your blood glucose. Of course, this also depends on what you ate, but it should give you some information.

Testing before and after bed helps show you whether your basal insulin might be adjusted.

Interpreting the data

I am not a doctor. Seriously, I won’t stop saying this. Talk to a doctor before you adjust your insulin dosage.

After having tested according to the schedule I mentioned above for a few days (try at least a week), you can start interpreting the data.

Here are a few observations and what I think they might mean:

Blood glucose consistently rises after a meal

If your blood glucose if always (or most of the time) higher after a meal than it was before, that might mean that you need more mealtime insulin. It might also mean that you are eating very fatty foods which take a longer time to digest.

Blood glucose consistently falls after a meal

If your blood glucose always goes down significantly after a meal, you are probably taking too much insulin. Adjusting your carb ratio so that you don’t take as much insulin could be helpful.

Blood glucose is always higher after bed than before

Your nighttime basal might be too low. If you go to bed a short time after eating, it might be related to carbs. Try eating earlier if this is the case.

Blood glucose is always lower after bed than before

Your nighttime basal might be too high.


I always try to keep my insulin ratio around 30% basal and 70% bolus. This works well for me because it keeps my blood glucose stable when I don’t eat, and allows me to accurately take insulin for meals and corrections. There are people who believe a ratio that more heavily favours basal insulin is better, and that’s fine. Diabetes treatment varies wildly from person to person.

All mealtimes can have different carb ratios. There is no reason for why you should have the same carb ratio at different times of the day.

tags: diabetes