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Adjusting Basal and Bolus Insulin Doses

A guide

· Type 1 Diabetes,Type 2 Diabetes,Diabetes,Insulin,Diabetes Support
If you notice your blood sugars are running high or low, knowing which insulin, basal or bolus to adjust and by how much to change insulin dosage by can be tricky. Adjusting insulin dosage is a skill which takes time to develop and comes through understanding.  Recording your numbers is well advised for making dosage change decisions. The information below can be used as a guide to how basal and bolus doses can affect your blood sugar.
Adjusting your long term, basal insulin dose

Also referred to as background insulin, basal insulin is the insulin which acts over most of the day, typically between 16 and 24 hours depending on which long term insulin you take.

If you are unsure about whether your background insulin needs changing, a good way to check is do a fasting test, which involves not eating and not injecting short term insulin for several hours.

Throughout the fast you can test your blood sugar at regular intervals, say once every two hours and observe whether your blood sugars are dropping or increasing.

If you increase your long term insulin, there’s a chance that you may start to have low blood sugars over night. 

If in doubt about this, or any other dosing decisions, check with your health care team before adjusting your doses.


Adjusting your short term, bolus insulin dose

Adjusting short term insulin is usually more straight-forward than adjusting long term insulin, however, care needs to be taken as mistakes with short term insulin dosage adjustments can be more severe. If you find that your blood sugars are high or low following a particular meal most days, you may wish to consider increasing or decreasing the short term insulin for that meal.

Say your numbers are generally good through the day with the exception that you notice a trend of numbers frequently above 9.0 mmols/l before your evening meal.

This indicates that your insulin dose at lunch is likely to be too small. It may be worth increasing your lunch time insulin in this case.


Having the right basal insulin program and setting the right doses is important for anyone who uses insulin. Taking too much basal insulin, or taking it at the wrong times, can result in frequent (and perhaps severe) hypoglycemia, not to mention weight gain. Taking too little basal insulin will produce high blood glucose and make it very difficult to set appropriate mealtime bolus doses. However, a properly set basal insulin level will allow you a great deal of flexibility in your schedule and should allow you to go to sleep confident about where you’ll be when you wake up.


Fine-tuning basal insulin can be complex, so don’t hesitate to ask a member of your health-care team for help with this task. An endocrinologist, certified diabetes educator, nurse practitioner, or insulin pump specialist can usually help you put your basal insulin on the right track. And don't forget to use the spike app for insulin reminders!

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