Insulin

Question 1

How does insulin work?

Answer 1

In diabetes mellitus, exogenous insulin functions similarly to endogenous insulin. It stimulates glucose uptake from the circulation into tissues, including skeletal muscle and fat, and increases use of glucose as an energy source. Insulin stimulates glycogen, lipid and protein synthesis and inhibits gluconeogenesis and ketogenesis. For the treatment of hyperkalaemia, insulin drives K+ into cells, reducing serum K+ concentrations. However, once insulin treatment is stopped, K+ leaks back out of the cells into the circulation, so this is a short-term measure while other treatment is commenced.

Where IV insulin is required (hyperkalaemia, diabetic emergencies, peri-operative glucose control), soluble insulin (Actrapid®) is usually used.

Question 2

Indications for insulin

Answer 2

For insulin replacement in people with type 1 diabetes mellitus and control of blood glucose in people with type 2 diabetes mellitus where oral hypoglycaemic treatment is inadequate or poorly tolerated.

Given intravenously, in the treatment of diabetic emergencies such as diabetic ketoacidosis and hyperglycaemic hyperosmolar syndrome, and for perioperative glycaemic control in selected diabetic patients.

Alongside glucose to treat hyperkalaemia, while other measures (such as treatment of the underlying cause) are initiated.

Question 3

Contraindications for insulin

Answer 3

In patients with renal impairment, insulin clearance is reduced, so there is an increased risk of hypoglycaemia.

Question 4

Side effects of insulin

Answer 4

Main: hypoglycaemia (which can be severe enough to lead to coma and death) 
Via subcutaneous (SC) injection at the same site, insulin can cause fat overgrowth (lipohypertrophy), which may be unsightly or uncomfortable.

Question 5

Interactions of insulin

Answer 5

Although often necessary, combining insulin with other hypoglycaemic agents increases the risk of hypoglycaemia. Concurrent therapy with systemic corticosteroids increases insulin requirements.

Question 6

Elimination of insulin

Answer 6

Renal

Question 7

Patient information on insulin

Answer 7

SC insulin is often administered using ‘pens’ containing insulin in solution (100 units/mL). These allow a patient to ‘dial up’ the number of units required and administer insulin discreetly, e.g. through clothes.

When starting a patient with diabetes mellitus on insulin, explain that insulin will help to control blood sugar levels and prevent complications. Advise them that lifestyle measures, including a calorie-controlled diet and regular exercise, are needed as well as insulin to improve health. Warn them of the risk of hypoglycaemia, advising them of symptoms to watch out for (e.g. dizziness, agitation, nausea, sweating and confusion). Explain that, if hypoglycaemia develops, they should take something sugary (e.g. glucose tablets or a sugary drink) then something starchy, e.g. a sandwich.