Type 2 Diabetes Mellitus - quality prescribing strategy: improvement guide 2024 to 2027

7. When to consider insulin therapy in type 2 diabetes mellitus?

Insulin is required by some people for treatment of T2DM, usually if other pharmacological therapy is no longer effective. Often this can be because of prolonged excess insulin secretion as a result of insulin resistance. It is not necessarily due to a failure of the individual to comply with their diet and/or treatment regimen.

Red flags for people requiring insulin urgently. These are:

• weight loss without dietary restriction;
• marked symptoms of hyperglycaemia despite increased diabetes treatment; or
• if self-glucose monitoring, continued high blood sugars despite increased diabetes treatment.

Insulin regimens should be adapted to the person considering lifestyle factors, carbohydrate counting and individual choice, with appropriate targets for glycaemic control. There are often psychological barriers to insulin therapy, and these should be considered. Other diabetes treatments should be reviewed and discontinued where appropriate, but metformin, if tolerated, should always be continued.

Human isophane insulin is recommended as the first-choice regimen. Long-acting insulin analogues should not be considered unless the patient experiences recurrent episodes of hypoglycaemia, or requires assistance with insulin injection. For most people with T2DM, long-acting insulin analogues offer no significant benefit over human isophane insulin and are more expensive. For a full list of insulins available in the UK see Insulins in the UK list.

Insulin therapy in order of increasing complexity:

1. Once or twice daily intermediate (NPH) human insulin

2. Once daily long-acting insulin analogue

3. Once or twice daily mixed human insulin (normally 25 or 30% quick acting insulin)

4. Once or twice daily intermediate human; or once daily long-acting insulin analogue, with once daily quick acting human insulin taken before main meals (basal plus regimen)

5. Once daily long-acting insulin analogue with pre-prandial quick acting insulin (basal bolus or multiple daily injection).