When you forget to take your basal insulin injection, the rate of rise in blood sugar is individual and depends on the type and dose of insulin. If you are unsure how to proceed in this situation, contact your care provider.
Forgetting to take basal insulin injection
If you forget to take your basal insulin injection, your blood sugar will begin to rise as the effect of the previous injection wears off. What should you do then?
If you are uncertain whether you took your basal insulin dose or not, it is recommendable to use rapid-acting insulin to take care of the situation, to avoid accidentally taking the basal insulin twice. Check your blood sugar or the sensor reading immediately and then at least every 4 hours. If you are not feeling well or if your blood sugar is higher than 14 mmol/l, check your blood ketone level.
If your blood sugar is high, for example, above 10 mmol/l, correct it with bolus insulin in accordance with your insulin sensitivity factor. For instance, if 1 unit of bolus insulin lowers your blood sugar by 2 mmol/l, you can take 2–3 units of bolus insulin to correct a blood sugar of 14 mmol/l.
Monitor your well-being. If your blood sugar cannot be controlled with rapid-acting insulin, ketones increase, or if your general health otherwise deteriorates, seek emergency care.
Take a rapid-acting insulin correction dose to correct high blood sugar. Take a reduced amount of basal insulin, i.e. the amount corresponding with its remaining hours. Take the next basal insulin injection at the normal time, using the normal dose.
Alternatively, you can offset the missing basal insulin by taking a small dose of bolus insulin every 4 hours until your next basal insulin injection.
Monitor your well-being. If your blood sugar does not normalize, ketones increase, or if your general health otherwise deteriorates, seek emergency care.
The usual dose of basal insulin is normally 12 units in the morning around 07–08 and 10 units in the evening between 21–23. You notice in the afternoon at 15 that your blood sugar is 16 mmol/l, even though you have taken your regular mealtime insulin doses. Measure ketones if you have a ketone meter. If you are certain that you forgot to take your morning basal insulin, in addition to correcting the high blood sugar with rapid-acting insulin, you can take a dose of basal insulin equivalent to the remaining hours from 15 to 21, which is 6 hours, amounting to 5 units (12 units / 13 hours x 6 hours = 5.4 units).
The normal dose of basal insulin is usually 20 units between 21–22 in the evening. Your blood sugar level in the morning at 07 is 20 mmol/l. Measure ketones if you have a ketone meter. If you are certain that you forgot your basal insulin injection the previous evening, in addition to correcting high blood sugar with rapid-acting insulin, you can take a dose of basal insulin equivalent to the remaining hours from 07 in the morning to 21 in the evening, which is 14 hours, totaling 11 units (20 units / 24 hours x 14 hours = 11.6 units).
The effect of degludec insulin lasts for over a day. If its injection is delayed or forgotten, take the normal dose as soon as you remember. Afterwards, you can continue dosing according to the regular schedule. However, note that there must be at least 8 hours between degludec injections.
If you suspect that you've forgotten to take the basal insulin
If you are uncertain whether you took your basal insulin dose or not, it is recommendable to use rapid-acting insulin to take care of the situation, to avoid accidentally taking the basal insulin twice. Check your blood sugar or the sensor reading immediately and then at least every 4 hours. If you are not feeling well or if your blood sugar is higher than 14 mmol/l, check your blood ketone level.
If your blood sugar is high, for example, above 10 mmol/l, correct it with bolus insulin in accordance with your insulin sensitivity factor. For instance, if 1 unit of bolus insulin lowers your blood sugar by 2 mmol/l, you can take 2–3 units of bolus insulin to correct a blood sugar of 14 mmol/l.
Monitor your well-being. If your blood sugar cannot be controlled with rapid-acting insulin, ketones increase, or if your general health otherwise deteriorates, seek emergency care.
If you are certain, that you've forgotten to take basal insulin
Take a rapid-acting insulin correction dose to correct high blood sugar. Take a reduced amount of basal insulin, i.e. the amount corresponding with its remaining hours. Take the next basal insulin injection at the normal time, using the normal dose.
Alternatively, you can offset the missing basal insulin by taking a small dose of bolus insulin every 4 hours until your next basal insulin injection.
Monitor your well-being. If your blood sugar does not normalize, ketones increase, or if your general health otherwise deteriorates, seek emergency care.
Example with basal insulin that is taken twice a day:
The usual dose of basal insulin is normally 12 units in the morning around 07–08 and 10 units in the evening between 21–23. You notice in the afternoon at 15 that your blood sugar is 16 mmol/l, even though you have taken your regular mealtime insulin doses. Measure ketones if you have a ketone meter. If you are certain that you forgot to take your morning basal insulin, in addition to correcting the high blood sugar with rapid-acting insulin, you can take a dose of basal insulin equivalent to the remaining hours from 15 to 21, which is 6 hours, amounting to 5 units (12 units / 13 hours x 6 hours = 5.4 units).
Example of basalinsulin that is taken once a day:
The normal dose of basal insulin is usually 20 units between 21–22 in the evening. Your blood sugar level in the morning at 07 is 20 mmol/l. Measure ketones if you have a ketone meter. If you are certain that you forgot your basal insulin injection the previous evening, in addition to correcting high blood sugar with rapid-acting insulin, you can take a dose of basal insulin equivalent to the remaining hours from 07 in the morning to 21 in the evening, which is 14 hours, totaling 11 units (20 units / 24 hours x 14 hours = 11.6 units).
The effect of degludec insulin lasts for over a day. If its injection is delayed or forgotten, take the normal dose as soon as you remember. Afterwards, you can continue dosing according to the regular schedule. However, note that there must be at least 8 hours between degludec injections.
Updated 7.3.2025