Common name in Nepal: Human Mixtard, Actrapid, Insugen, Lantus (glargine), NovoRapid (aspart), Human Insulatard (NPH)
What Is Insulin?
Insulin is the hormone that the body itself is deficient in or resistant to in diabetes, and injectable insulin therapy is the most effective glucose-lowering treatment available. In type 2 diabetes, insulin is typically added when oral medications and lifestyle measures are no longer sufficient to control blood sugar, when HbA1c is very high (commonly above 9-10%) at diagnosis, or when there are symptoms of significant hyperglycemia such as unintentional weight loss, excessive thirst, or ketosis.
Mechanism of Action
Injected insulin directly replaces or supplements the body's own insulin, binding to insulin receptors on muscle, fat, and liver cells to promote glucose uptake into cells and suppress the liver's glucose production. Different insulin formulations are designed to act on different timescales: basal (long-acting) insulins such as glargine, detemir, degludec, or NPH provide a steady background level to control fasting and between-meal glucose by suppressing excess liver glucose output, while bolus (rapid- or short-acting) insulins such as aspart, lispro, or regular/soluble insulin are taken around mealtimes to cover the glucose rise from food. Premixed insulins combine both types in fixed ratios for convenience.
Benefits
Insulin is the most potent glucose-lowering therapy available and has no maximum effective dose ceiling — it can bring even very high blood sugar under control when other treatments cannot. It is essential and life-saving in type 1 diabetes, and highly effective in advanced type 2 diabetes. Some evidence suggests that early, intensive insulin use at diagnosis of type 2 diabetes can help preserve remaining pancreatic beta-cell function and, in some patients, allow a period of remission.
Side Effects
Hypoglycemia is the most significant risk of insulin therapy — since insulin lowers blood sugar regardless of the underlying cause, too high a dose, a missed or delayed meal, unusual physical activity, or alcohol can all trigger dangerously low blood sugar. This risk is higher with bolus/prandial insulin than with basal insulin alone, and higher still with human/NPH insulin compared with newer insulin analogues.
Weight gain is common with insulin therapy, particularly with higher doses and bolus/prandial regimens, related to insulin's role in promoting fat storage and reduced calorie loss through urine once blood sugar is controlled.
Injection-site reactions, including lipodystrophy (lumpy or shrunken fatty tissue) at repeatedly used injection sites, can occur with frequent injections in the same spot; this can also cause erratic insulin absorption, so rotating injection sites is important.
Fear, stigma, and burden of therapy — while not a physical side effect, needle fear, injection-related anxiety, and the practical burden of frequent dosing and monitoring are well-documented barriers that can affect how consistently people take their insulin, and are worth discussing openly with patients.
Precautions
Insulin doses should be adjusted gradually and carefully, typically reviewed every few days during initiation or intensification, based on home glucose monitoring results. Patients should be taught to recognize and treat hypoglycemia (typically with 15-20 grams of fast-acting glucose) and should always carry a fast-acting sugar source. Meals should not be skipped after taking bolus or premixed insulin. Injection sites should be rotated systematically (e.g., between abdomen, thighs, and upper arms) to reduce the risk of lipodystrophy and inconsistent absorption. Alcohol can increase hypoglycemia risk and should be used cautiously.
Required Tests: Before and After Starting
Before starting insulin, baseline HbA1c and kidney function are typically checked, since kidney function affects insulin clearance and dosing needs. Home blood glucose monitoring (fasting, pre-meal, and sometimes post-meal readings) is essential during dose titration and ongoing therapy, and is the main day-to-day tool for adjusting insulin safely. HbA1c is generally rechecked every 3 to 6 months to assess overall control, and injection sites should be examined periodically for signs of lipodystrophy.
Sources
American Diabetes Association. "Standards of Care in Diabetes—2026." Diabetes Care, pmc.ncbi.nlm.nih.gov/articles/PMC12690185/
American Academy of Family Physicians. "Type 2 Diabetes Mellitus: Outpatient Insulin Management." American Family Physician, 2018.
Kalra S, et al. "The Modern Role of Basal Insulin in Advancing Therapy in People With Type 2 Diabetes." Diabetes Care, 2025.
American Association of Clinical Endocrinologists / American College of Endocrinology consensus guidance on insulin therapy.