Supporting adults with type 1 diabetes

The use of insulin in type 1 diabetes is life-saving as it prevents the potentially life-threatening complication of diabetic ketoacidosis (DKA) by increasing glucose uptake to the adipose tissue and muscles. It also suppresses hepatic glucose release, therefore lowering blood glucose levels.

The long-term goal of insulin use is the prevention of diabetes-related complications, including microvascular complications (retinopathy, nephropathy and neuropathy) and macrovascular complications (cardiovascular disease, cerebrovascular disease and peripheral arterial disease).

There are three types of insulin available in the UK: human insulin, human insulin analogues and rarely used animal insulin. Insulins are categorised according to their time-action profiles: time to peak, onset of action and duration of action (see Table 1). 

• Short acting, rapid acting and ultra-rapid acting insulins mimic the physiological secretion of insulin that occurs in response to the sharp rise of glucose following the ingestion of food or drink. These insulins are also known as prandial or bolus insulin.
• Intermediate, long acting and ultra-long acting insulins mimic the effect of basal insulin that is continuously released from the liver and is relatively constant but declines slightly during the night and peaks just before dawn. These insulins are also known as basal insulin.

All patients with type 1 diabetes should be offered a basal-bolus insulin regimen comprising multiple daily injections. The short or rapid acting insulin is injected before meals and basal insulin is injected once or twice daily, depending on the insulin. The first-line choice of basal insulin in type 1 diabetes is twice-daily insulin detemir. 

However, an alternative option can be considered:

• If the patient is already on a different basal insulin and is meeting his or her agreed treatment goal 
• If insulin detemir is not tolerated or the patient has a strong preference for once‑daily basal injections, then once-daily insulin glargine can be considered 
• If there is a concern about nocturnal hypoglycaemia or patients need help from a carer or healthcare professional to administer injections, once-daily insulin degludec can be considered.

Rapid acting insulin analogues should be offered first-line to all patients with type 1 diabetes over rapid acting soluble human or animal insulins as bolus insulin.

Although newly diagnosed patients should not be offered insulin regimens other than a basal-bolus one, there may be circumstances where an alternative regimen, such as twice daily premixed, may be considered.  

Overall, premixed insulins are not appropriate for patients with type 1 diabetes because the independent adjustment of the basal and bolus components are not possible. However, these insulins may be considered in those patients who simply prefer this simpler regimen. If this is the case, then a twice-daily premixed human insulin preparation is considered first-line. 

The twice-daily premixed analogue insulins can be considered if the patient is having recurrent hypoglycaemia that is affecting their quality of life.

Some patients with type 1 diabetes manage their blood glucose levels with an insulin pump – a small electronic device that releases insulin at a regular rate throughout the day. This device is a treatment option for those aged ≥12 years whose attempts to achieve a HbA1c target with a basal-bolus regimen have resulted in hypoglycaemia with a significant impact on quality of life, or for those whose HbA1c levels remain high despite being motivated, on a basal-bolus regimen, carbohydrate counting (see later) and checking blood glucose levels ≥ four times daily. 

These patients should only continue using a pump if it results in a sustained fall in HbA1c levels and/or a reduction in the frequency of hypoglycaemia episodes. 

The pump uses short acting or rapid acting insulin and provides a basal rate of insulin and delivers mealtime bolus dosing. However, the patient must still measure blood glucose frequently in order to adjust the pump to deliver the appropriate amount of insulin. Therefore the use of an insulin pump requires access to trained healthcare professionals in pump therapy and a motivated patient to manage their diabetes.

Newer insulin pumps can link with continuous glucose monitoring (CGM) to further improve glycaemic control and quality of life for patients with type 1 diabetes. Such systems are called closed loop systems.