The approach used to adjust insulin will be influenced by your insulin regimen (the type and amount of insulin taken).

Most people with type 1 will be advised to start a basal-bolus or multiple daily injection (MDI) regimen. This is the most flexible way of insulin management; ideal if you have a busy life, with lots of different activities going on. 

Adjusting your insulin does depend on which regime you use, but there are some useful general guidelines that apply to everyone: 

Remember that insulin will lower your blood glucose, so if you take too much insulin your blood glucose can go too low and if you take too little it can go too high.

Regular blood glucose testing and recording the results will help you to see how your blood glucose levels change and allow you to improve your overall diabetes management.

Unless you are confident with self-adjusting insulin, it’s recommended to factor in dosage changes gradually as making larger adjustments could lead to an increased chance of dosing error.

You are likely to be adjusting your quick-acting insulin doses on a daily basis. On the other hand, you should only adjust your basal (long-acting insulin) doses occasionally, and this is usually worth discussing with your diabetes team. 

See below for guidance for adjusting basal and bolus insulin:

Some indicators that your long-acting (basal insulin) is not the correct dose include:

  • Blood glucose is consistently high or low across the whole 24 hours period
  • Blood glucose levels are always high or always low in the morning;

The only insulin working overnight is your basal insulin. Glucose level should stay fairly steady overnight if the dose is correct. If glucose consistently rises overnight, it is likely that your basal insulin dose is too low if glucose consistently falls overnight, it is an indication that your basal insulin dose may be too high.

Another way to assess whether your basal insulin dose is correct is to have a carb-free/ insulin-free lunch, and look at whether your glucose levels rise or fall over the afternoon.  As you have no short-acting insulin on board, any change in glucose must be due to the basal insulin; too little insulin and glucose will rise, too much insulin and glucose will fall.

Once you are sure there is a definite pattern, you could make a small adjustment to your basal dose and recheck. If you are not confident in doing this, then speak with your healthcare team.

Your short-acting insulin (bolus insulin) is what you will be adjusting on a day-to-day basis, depending on the amount of carbohydrate you eat and in response to your blood glucose levels.

If your blood glucose is regularly rising after meals, then it probably means you are not taking enough insulin to cover the carbohydrate eaten in the meal. Find out more about carb counting and insulin adjustment in our 'carbohydrate counting' topic.

Spotting patterns

Identifying repeating patterns is so important; Is your blood glucose always high or always low at a certain time of the day? or after a certain type of food or exercise? Adjust your insulin proactively to stop it from happening again.  

Points to note

It's important to remember that:

Always think back to the last insulin dose and consider if that dose needs to be altered over the coming days and weeks.

Rather than constantly ‘correcting’ high blood glucose, you should consider why your glucose went high in the first place and proactively change your insulin over the coming days to prevent the same thing from happening again.