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Insulin
Antidiabetic — Insulin HormoneNigerian brand names:ActrapidHumulin RHumulin NMixtardLantusToujeoNovomix
Reviewed by the PMC Medical Team · Promise Medical Centre
Overview
Insulin is a hormone naturally produced by the pancreas that allows cells to take up glucose from the blood for energy. In diabetes, either the pancreas does not produce enough insulin (Type 1 diabetes — absolute deficiency) or the body's cells do not respond effectively to insulin (Type 2 diabetes — relative deficiency with insulin resistance). Insulin therapy is absolutely essential for all people with Type 1 diabetes and for many people with Type 2 diabetes whose blood sugar cannot be controlled with oral medications alone. Multiple types of insulin exist, differing in how quickly they act and how long they last.
Uses
Insulin is used to:
- Type 1 diabetes: Lifelong insulin is required — the pancreas produces no insulin
- Type 2 diabetes: When blood sugar cannot be controlled with lifestyle changes and oral medications (metformin, etc.) alone
- Gestational diabetes: When blood sugar in pregnancy cannot be controlled with diet and exercise alone — insulin is the preferred pharmacological treatment in pregnancy (metformin is an alternative)
- Diabetic ketoacidosis (DKA): Medical emergency requiring hospital IV insulin
- Hyperosmolar hyperglycaemic state (HHS)
- Any severely ill diabetic patient: Stress hyperglycaemia during surgery, infection, or hospitalisation often requires temporary insulin
Types of insulin (commonly available in Nigeria):
- Short-acting (Regular/Actrapid): Onset 30 min, peak 2–4 h, duration 6–8 h — given before meals
- Intermediate-acting (NPH/Humulin N, Mixtard): Onset 1–4 h, duration 10–18 h — given once or twice daily
- Long-acting (Glargine/Lantus, Detemir): Onset 2 h, no pronounced peak, duration ~24 h — once daily basal insulin
How to Use
Insulin must be injected — it cannot be taken by mouth as stomach acid destroys it.
Injection sites: Abdomen (fastest absorption), thighs, buttocks, upper arms. Rotate injection sites within the same area to prevent lipohypertrophy (fatty lumps).
How to inject:
1. Wash hands thoroughly
2. Check insulin type and expiry date carefully
3. For cloudy insulins (NPH, Mixtard): Roll the vial gently between palms 10 times; do not shake
4. Clean injection site with alcohol swab; let it dry
5. Pinch the skin, insert needle at 90° (45° if thin), inject slowly, hold for 10 seconds, withdraw
6. Dispose of needle in a sharps container immediately — never reuse needles
Timing:
- Short-acting insulin: Inject 30 minutes before meals
- Rapid-acting analogues (Novorapid, Humalog): Inject immediately before meals
- Long-acting insulin (Lantus/Glargine): Same time each day, regardless of meals
Dosing: Highly individualised — determined and adjusted by your doctor based on blood sugar monitoring results. Never adjust your own dose without medical guidance.
Side Effects
Most important — Hypoglycaemia (low blood sugar): The most common and potentially dangerous side effect of insulin:
- Mild: Sweating, trembling, hunger, dizziness, palpitations — treat immediately with fast sugar (glucose tablets, sugary drink, sugar lumps)
- Severe: Confusion, seizures, unconsciousness — requires glucagon injection or emergency medical care
- Always carry glucose tablets or sugar with you. Wear a medical ID bracelet. Inform family and colleagues
Other side effects:
- Injection site reactions: Redness, swelling, itching (usually temporary)
- Lipohypertrophy (fatty lumps): Caused by injecting into the same spot repeatedly — rotate sites
- Weight gain: A common effect of insulin therapy
- Oedema (fluid retention) when starting insulin
- Visual changes when starting therapy: Temporary (lens swelling due to fluid shifts)
Warnings & Precautions
Critical safety points for insulin use:
- Check insulin type before every injection: Different insulins look alike (clear vs cloudy) but work very differently. Giving the wrong type can cause dangerous hypoglycaemia or very high blood sugar. Double-check the label every single time
- NEVER shake insulin: Rolling is sufficient for cloudy insulins; shaking creates bubbles that alter dosing
- Do not mix insulins unless specifically directed: Mixing incompatible insulins can alter their properties and action times
- Insulin storage: Open/in-use vials can be kept at room temperature (see Storage below); unopened vials must stay refrigerated
- Sick day rules: During illness (fever, vomiting, diarrhoea), blood sugar often rises even if eating less — do not stop insulin; check blood sugar more frequently; contact your diabetes team
- Driving: Do not drive if blood sugar is below 5.0 mmol/L (90 mg/dL) or if you feel hypoglycaemic
- Alcohol: Alcohol inhibits the liver's ability to release glucose, increasing hypoglycaemia risk — especially when drinking without eating
- Pregnancy: Insulin requirements change significantly during pregnancy — close monitoring and dose adjustment are essential
Drug Interactions
Important interactions:
- Other antidiabetic drugs (metformin, glipizide, empagliflozin): Additive blood-sugar lowering — dose adjustment of insulin may be needed; increased hypoglycaemia risk
- Beta-blockers (atenolol, propranolol): Can mask symptoms of hypoglycaemia (hide sweating, palpitations, tremor) — hypoglycaemia may be unrecognised; also prolong hypoglycaemia recovery
- ACE inhibitors: May enhance insulin sensitivity — risk of hypoglycaemia
- Corticosteroids (prednisolone, dexamethasone): Raise blood sugar significantly — insulin dose usually needs to increase during steroid courses
- Thiazide diuretics (hydrochlorothiazide): Can raise blood sugar — monitor glucose
- Alcohol: Increases hypoglycaemia risk, especially on an empty stomach
- Salicylates (high-dose aspirin): Can lower blood sugar — monitor
- Sympathomimetics (salbutamol, adrenaline): Can raise blood sugar — monitor glucose during acute illness or asthma treatment
Storage
Unopened insulin vials/cartridges: Refrigerate at 2–8°C (do NOT freeze — freezing destroys insulin). Keep away from the freezer compartment.
In-use (opened) vials: Can be kept at room temperature (below 30°C) for up to 28 days (check individual product guidance — some are 30 or 42 days). Keep away from direct heat and sunlight.
Do not use insulin that has changed colour, become cloudy (for clear insulins), or shows any particles. Check before every use.
Keep out of reach of children.
Buy only NAFDAC-registered medications
Nigeria has a significant problem with counterfeit and substandard drugs. Always purchase medications from a licensed pharmacy and check the NAFDAC registration number on the package — verify at nafdac.gov.ng.