Never change an insulin dose or type on your own. This page explains what your regimen is doing; the numbers in it come from your care team.
The types
| Type | Starts | Peaks | Lasts |
|---|---|---|---|
| Ultra-rapid (faster aspart) | 2–5 min | ~1 h | 3–5 h |
| Rapid (aspart, lispro, glulisine) | 10–20 min | 1–2 h | 3–5 h |
| Regular / short (human) | 30 min | 2–4 h | 6–8 h |
| Intermediate (NPH) | 1–2 h | 4–8 h | 12–18 h |
| Long (glargine, detemir) | 1–2 h | minimal | 20–24 h |
| Ultra-long (degludec, glargine U300) | 1–2 h | flat | >40 h |
Basal and bolus
Basal insulin covers the glucose your liver releases continuously, day and night. It is correct when your glucose stays roughly level while you are not eating — the classic test is checking that you neither drift up nor drop overnight.
Bolus insulin covers a meal, or corrects a high. Two ratios define it:
- ICR — insulin-to-carb ratio. Grams of carbohydrate covered by one unit. An ICR of 10 means one unit per 10 g.
- ISF — insulin sensitivity factor. How far one unit lowers your glucose. An ISF of 50 means one unit drops you about 50 mg/dL.
Starting estimates come from the 500 and 1800 rules — ICR ≈ 500 ÷ total daily dose, ISF ≈ 1800 ÷ total daily dose — but these are only a first guess to be refined against your actual readings, by your doctor.
Timing is a dose in itself
Rapid insulin injected at the first bite is already behind the food. Most people get a noticeably lower post-meal peak by injecting 15–20 minutes before eating — the same dose, better matched. Exceptions: if you are already low, if you are unsure you will finish the meal, or if gastroparesis slows your digestion.
Technique details that matter
- Rotate sites. Repeatedly injecting the same spot causes lipohypertrophy — firm lumps under the skin where absorption becomes slow and unpredictable. This is one of the most common hidden causes of erratic control. Feel your sites; if you find a lump, stop using it and tell your doctor, because your dose may need reducing once you move to healthy tissue.
- Absorption speed varies by site: abdomen fastest, then upper arm, then thigh, then buttock.
- Use a new needle each time. Reused needles blunt, hurt more, and damage tissue.
- Count to ten before withdrawing a pen needle, or part of the dose leaks back out.
- Prime 2 units before each pen injection to clear air.
- Cloudy insulins (NPH, mixes) must be resuspended — roll and tip gently 20 times. An unmixed dose can be wildly off.
Storage — and heat
Unopened insulin belongs in the fridge at 2–8°C. Never freeze it; frozen insulin is destroyed and must be discarded. In use, a pen or vial can stay at room temperature for about 28 days, which is more comfortable to inject.
Heat is the real problem in an Iraqi summer. Above roughly 30°C insulin loses potency, and a car interior reaches far more than that within minutes. Unexplained highs across a whole week, with no change in food or dose, are sometimes nothing more than a pen that spent an afternoon in the sun. Use an insulated pouch or an evaporative cooling wallet when travelling, and keep supplies away from windows.