Insulin adjusting

When you are ill your blood glucose levels tend to be erratic and often higher than usual. It’s important to know how to adjust your insulin doses accordingly so that your blood glucose settles down and allows you to recover from your illness. 

The way you adjust your insulin depends on the type of insulin you use. You may have been told to adjust your insulin doses after seeing a pattern in your glucose levels for three days. If you are ill, however, you might need to adjust your doses right away. 

Whichever type of insulin you take: 

Basal bolus or four-times-daily insulin  

If you are unwell and your blood glucose levels are high or erratic, you should use the same principle as described earlier to adjust your insulin, reflecting on patterns (see section 3; adjusting insulin doses). 

Here are some specific guidelines for sick days: 

• You can also take a correction dose of insulin if your blood glucose is high. Your diabetes care team will advise you on this. If you already have an insulin sensitivity factor (ISF), and you know how much 1 unit of insulin will lower your blood glucose by, then use those principles to take extra insulin, otherwise follow the flow chart (below) to work out how much extra insulin to take and when. 

• You can also give yourself a correction dose in between meals if your blood glucose is high, but be careful if this is within 3-4 hours of a previous injection, as you may still have insulin on board and may be at risk of having a hypo. Always wait at least 2 hours between quick-acting doses. 

• If your blood glucose levels are consistently high (in the morning and throughout the day) you might want to increase your long-acting insulin. A lot of long-acting insulin works for about 24 hours. Be careful not to increase it too much, however, as you could then be at risk of having night-time hypos. 

Sick Day Flow Chart and Guidance for People using Basal-Bolus Insulin 

This flow chart should take you through the steps of what to do if you are unwell. The accompanying info sheet describes this further. 

Click here for an example of how insulin should be adjusted when using the basal-bolus method.

Twice-daily insulin 

The sick day flow chart is designed for people using basal-bolus insulin (short and long-acting insulin injections). If you use twice a day ‘mixed insulin’ (which could include Novomix30, Humalog 25, Humulin M3), you should follow general insulin adjustment guidance given in section 3, but may need to make more frequent adjustments during illness   

• Your injection at breakfast time will affect your lunch and evening meal blood glucose levels and anything in between. 

• Your injection with your evening meal injection will affect your bedtime and breakfast time blood glucose levels and anything in between. 

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Have a look at the following example of how to adjust insulin when using twice-daily injections method.