Reviewed by MedNext Clinical Team
Insulin therapy remains the cornerstone of type 1 diabetes management and is frequently required in type 2 diabetes when oral agents are insufficient. Understanding the pharmacokinetic profiles of different insulin formulations is fundamental to safe initiation and dose adjustment [1].
Basal Insulin
Basal insulins are designed to provide steady background coverage over 24 hours, suppressing hepatic glucose output between meals and overnight. Long-acting analogues such as insulin glargine and insulin detemir have a relatively flat pharmacokinetic profile with minimal peak effect, reducing nocturnal hypoglycaemia risk compared to older NPH insulin [1]. Insulin degludec offers an even longer duration of action, exceeding 42 hours, which allows flexible dosing timing.
Bolus (Rapid-Acting) Insulin
Rapid-acting analogues — insulin aspart, lispro, and glulisine — are used to cover mealtime glucose excursions. They begin working within 15 minutes, peak at 60–90 minutes, and last 3–5 hours. Patients should ideally inject immediately before meals or up to 15 minutes before eating. Ultra-rapid formulations (e.g., faster aspart) are now available with an even quicker onset.
Mixed Insulin Regimens
Premixed insulins (e.g., biphasic insulin aspart 30) combine a rapid-acting component with an intermediate-acting component in fixed ratios. They are convenient for patients who prefer twice-daily dosing but offer less flexibility for dose titration. They are often used in type 2 diabetes when a simple regimen is preferred.
Hypoglycaemia Awareness
All insulin regimens carry a risk of hypoglycaemia. Patients must be educated on recognition and treatment of hypoglycaemia before insulin is initiated. Key risk factors include missed meals, unexpected physical activity, alcohol consumption, and dose errors. Glucagon emergency kits should be prescribed for all patients on insulin who live with others.
Sick Day Rules
Patients must understand never to stop insulin during illness, even if not eating — insulin requirements often increase during intercurrent illness due to counter-regulatory hormone responses. Specific sick day guidance should be provided at initiation and reinforced at every review.
Storage and Handling
Unopened insulin should be stored in a refrigerator (2–8°C). In-use pens and vials can be kept at room temperature (below 25–30°C depending on formulation) for up to four weeks. Insulin should never be frozen or exposed to direct sunlight. Cloudy rapid-acting insulins should be discarded.
References
- DeWitt DE, Hirsch IB. Outpatient insulin therapy in type 1 and type 2 diabetes mellitus. JAMA. 2003;289(17):2254-2264.