Insulin regimens

The appropriate insulin regimen for each patient with diabetes will depend on their type of diabetes and their individual needs and circumstances. For example, a younger patient with uncontrolled diabetes may require more active management than a patient with the same poor diabetes control who is older, more frail, or has another life-limiting illness. See the separate Diabetes education and self-management programmes article.

Insulin regimens should be tailored to the individual, taking into account the patient's type of diabetes, previous control, age, dexterity, eyesight, and personal and cultural preferences.

Insulin is usually injected into the upper arms, thighs, buttocks or abdomen. The absorption may be increased if the limb is used in strenuous exercise after the injection. Lipodystrophy can be minimised by using different injection sites in rotation. Local allergic reactions may occur but are rare.¹

Effective patient education for people using insulin treatment is essential and should include the following: ²

• 'Sick day' guidance. See also the separate Diabetes and intercurrent illness article. Insulin Passports and patient information booklets should be offered to patients receiving insulin.

• Injection technique and the need to rotate injection sites.

• Self-monitoring where needed.

• Dietary advice.

• Advice on fitness to drive.

• How to manage hypoglycaemia.

Types of insulin^{1 2}

Insulins are classified according to their duration of action.

Short-acting insulins

• Short-acting (soluble) insulin is usually injected 15-30 minutes before meals. Soluble insulin is also the most appropriate form of insulin for use in diabetic emergencies - eg, diabetic ketoacidosis and at the time of surgery.

• When injected subcutaneously, soluble insulin has a rapid onset of action (30-60 minutes), a peak action between two and four hours, and a duration of action of up to eight hours.

• The rapid-acting human insulin analogues (insulin aspart, insulin glulisine and insulin lispro) have a faster onset and shorter duration of action than soluble insulin. Subcutaneous injection of insulin analogues can be injected shortly before or even after a meal. They can also help those susceptible to hypoglycaemia before lunch and those who eat late in the evening and are prone to nocturnal hypoglycaemia.

Intermediate-acting

• Subcutaneous injections of intermediate-acting insulins have an onset of action of approximately 1-2 hours, a maximal effect at 3-12 hours and a duration of 11 - 24 hours.

• Examples include isophane insulin.

Long-acting insulins

• These may last up to 36 hours; a steady state level is achieved after 2-4 days of use.

• Examples include protamine zinc insulin, insulin zinc suspension, insulin detemir, insulin glargine and insulin degludec.

Biphasic insulins

• These are pre-mixed preparations which contain a combination of a short and intermediate acting insulin.

• Patients do not nowadays mix two types of insulin together themselves, instead they are given a pen with the appropriate single or pre-mixed insulin in it.

Insulin regimens

Only regimens for type 2 diabetes will be discussed in detail here, as type 1 diabetes is largely managed in secondary care.

The choice of regimen will depend on a variety of factors, including:

• The patient's preference as to the number of times per day that they inject.

• Whether they can self-inject or need help from a relative or healthcare professional.

• If there is a concern about nocturnal hypoglycaemia.

Potential regimens include the following:

• Human isophane insulin injected once or twice a day. If hypoglycaemia is problematic on this regimen then a switch to insulin detemir or insulin glargine might be useful.

• Human isophane insulin combined with a short-acting insulin.

• Insulin detemir or glargine injected once daily. The long-acting nature of these insulins can be helpful for those who cannot inject themselves (eg, due to frailty) as the once daily regimen reduces the number of visits from a healthcare professional to help with injecting.

• A biphasic preparation with a short and intermediate acting insulin, injected before breakfast and before the evening meal - this is useful for patients who prefer to inject directly before a meal, or when hypoglycaemia is an issue, or if blood sugar rises significantly after meals.

• A basal-bolus regimen; intermediate- or long-acting insulin at bedtime, with short-acting insulin before meals. This gives the most flexibility.

Continuous subcutaneous insulin infusion (CSII) therapy, or insulin pump therapy

In CSII therapy, an adjustable basal infusion rate of insulin is given via an indwelling catheter, supplied from a syringe reservoir worn underneath the patient's clothing. The patient can then activate pre-meal boluses. Pumps can be disconnected for short periods (up to one hour) for activities such as swimming. They can be pre-programmed - for example, to compensate for nocturnal and early morning glucose fluctuations. The rate of insulin absorption from pumps is more predictable than with multiple subcutaneous injections. CSII therapy is particularly useful for patients with recurrent hypoglycaemia, unpredictable lives, delayed meals or pre-breakfast hyperglycaemia.

The insulin used in pumps may be soluble or a fast-acting analogue. Note that there have been two anecdotal case reports of insulin lispro precipitating in pumps: if users have unpredictable glucose fluctuations, they should consider changing to aspart or soluble insulin. It is only used in those with type 1 diabetes and will not be discussed further in this leaflet.

Adults with type 2 diabetes

The National Institute for Health and Care Excellence (NICE) recommends:²

When starting insulin therapy in adults with type 2 diabetes:

• Continue to offer metformin for people who are already taking it, but stop other medicines being used solely to manage hyperglycaemia.

• Offer basal insulin injected once or twice daily according to need.

• Consider combining basal and short-acting insulin (particularly if the person's HbA1c is 75 mmol/mol (9.0%) or higher), administered either separately or as a pre-mixed (biphasic) human insulin preparation.

• Consider pre-mixed (biphasic) preparations that include short-acting insulin analogues, rather than pre-mixed (biphasic) preparations that include short-acting human insulin preparations, if a person prefers injecting insulin immediately before a meal or hypoglycaemia is a problem or blood glucose levels rise markedly after meals.

• Decisions on insulin therapy should be made using a shared decision-making principle, based on considerations including concerns about hypoglycaemia, the need for assistance with injecting and any strong preference for once-daily injections.

• The least expensive option should be used if multiple types are available.

Pregnancy

Good glycaemic control is especially important both pre-conception and antenatally, to reduce fetal abnormalities and obstetric complications. Insulin must be continued for patients with type 1 diabetes and is often required in type 2 and gestational diabetes.

See the separate Diabetes in pregnancy article.

Insulin management around surgery

See the separate Precautions for patients with diabetes undergoing surgery article.

In practice, treatment should be tailored to the individual, taking into account lifestyle, preferences, and personal patterns of glycaemic control. Whatever the insulin regimen, patient education, and involvement are crucial in achieving good results.