Basal Insulin Initiation

Basal insulin is started in type 2 diabetes when oral and non-insulin injectable drugs do not achieve the target, or when glucose is markedly elevated with symptoms, and it is the first insulin step. It lowers fasting glucose with a low hypoglycaemia risk when titrated carefully. In type 1 diabetes it is always combined with mealtime insulin.

Insulin types. Intermediate (isophane/NPH), long-acting analogues (glargine U100, detemir), and ultra-long analogues (degludec, glargine U300).

Continuation. Keep metformin and organ-protective agents.

Choice. Human isophane insulin at bedtime is effective and cheap and is often the only option in East Africa. Long-acting analogues give less nocturnal hypoglycaemia and are preferred where affordable.

Indications. HbA1c over 86 mmol/mol (10%), symptoms of hyperglycaemia, catabolic weight loss, ketosis, pregnancy, or failure of other agents.

Sulphonylureas. Reduce the dose by 50% when starting basal insulin, or stop if hypoglycaemia occurs.

Safety checks. Confirm the patient can inject, store and dispose of insulin, test capillary glucose, and recognise and treat hypoglycaemia before the first dose.

Starting dose. 10 units subcutaneously once daily, or 0.1 to 0.2 units/kg daily. Use the lower end in older adults, kidney or liver impairment, and low body weight.

Timing. Give glargine, detemir or degludec at the same time each day. Give isophane insulin at bedtime (22:00) for morning fasting control.

Injection technique. Use 4 mm pen needles; rotate sites across the abdomen and thighs; a new needle for each injection; inspect sites for lipohypertrophy. Do not inject into lumps.

Storage. Keep unopened insulin refrigerated at 2 to 8 degrees Celsius; do not freeze. In-use pens and vials are kept under 30 degrees Celsius for up to 28 days (degludec up to 56 days). Where refrigeration is unreliable, keep in-use insulin away from direct sunlight and heat.

Conversion when changing preparation. From isophane twice daily to glargine once daily, use the same total daily dose; reduce by 20% if the isophane dose was high or hypoglycaemia occurred. From glargine U100 to degludec, use the same units.

Kidney impairment. Reduce dose by 25% when eGFR is 10 to 50, and by 50% when under 10.

Special groups. - Liver disease: use a low start dose of 0.1 units/kg and titrate slowly. - Pregnancy: isophane or detemir are used; specialist titration. - Breastfeeding: compatible. - Older adults: start at 0.1 units/kg or lower, with relaxed fasting targets. - Children: type 1 diabetes dosing is weight based and specialist led.

Monitoring. Fasting capillary glucose daily during titration. HbA1c at 3 months. Review injection sites at every visit.

Hypoglycaemia plan. Teach treatment with 15 to 20 g fast-acting carbohydrate, and give relatives instructions for glucagon 1 mg intramuscularly where supplied.

Stopping. Stop or reduce for recurrent glucose under 4 mmol/L, or unexplained weight loss with falling insulin need.

Referral and escalation. Refer if dose exceeds 0.5 units/kg without control, if hypoglycaemia is recurrent, or if ketones appear.