Adjusting insulin for type 1 diabetes during acute illness

Patients with type 1 diabetes who become unwell may be managed at home if the illness is not accompanied by persistent nausea, vomiting, ketosis, worsening hyperglycaemia or recurrent hypoglycaemia (see Symptoms indicating a patient with diabetes and an acute illness needs hospital referral for symptoms indicating need for hospital referral).

In an acute illness, the basal insulin requirement typically increases. Supplemental (correction) doses of rapid- or short-acting insulin should be given every 2 to 4 hours, in addition to the patient’s usual prandial (mealtime) bolus insulin doses, to reduce hyperglycaemia and stop development of ketosis. For information about calculating supplemental doses of insulin, see Supplemental (correction) insulin doses.

In contrast, some patients with an acute illness such as gastroenteritis may develop hypoglycaemia; more frequent blood glucose concentration monitoring and appropriate management are required to avoid this. Even if the illness is accompanied by nausea, vomiting or marked anorexia, basal insulin should not be withheld or stopped regardless of whether it is given as a long-acting insulin injection or by continuous subcutaneous insulin infusion (CSII) pump because insulin deficiency can lead to DKA. However, a reduction in the usual basal insulin dose may be required.

Basal insulin dosage should usually be continued and prandial (mealtime) bolus insulin dosage may need to be reduced. If the patient can’t maintain their carbohydrate intake by eating their usual food, they should drink fluids containing glucose (eg carbonated drinks [may be less likely to trigger vomiting if ‘flat’], fruit juice). They may consider drinking oral rehydration solution (eg Gastrolyte, Hydralyte, Repalyte) to replace fluid and electrolytes. If vomiting occurs after a prandial bolus insulin dose has been given, the patient should have sips of glucose-containing drinks every 20 to 30 minutes while closely monitoring their blood glucose concentration.

If repeated episodes of hypoglycaemia occur or if the patient is unable to tolerate oral intake, they should seek urgent assistance.

Patients with type 1 diabetes who are using a CSII pump can develop ketosis and DKA more rapidly because they do not have a background reservoir of long-acting insulin. They require more frequent blood glucose concentration monitoring during episodes of acute illness. A short-term increase or decrease in basal rate may be required using a temporary basal rate setting on their CSII pump.

Patients using CSII pumps must be able to identify and manage problems with insulin pump delivery. They must have an emergency action plan, including directions for use of and ready access to prefilled insulin injector pens for a change to a multiple daily injection (basal–bolus) insulin regimen. See Disruption of pump–delivered subcutaneous insulin for information about CSII pump delivery problems and using an alternative insulin regimen when insulin delivery from a CSII pump is interrupted.