Insulin: Types, Dosing, and Practical Tips

If you use insulin or care for someone who does, you already know it’s powerful and precise. This page explains the common insulin types, when to take them, how to avoid low blood sugar, and simple storage and injection tips you can use every day.

Know the insulin types and timing

Insulin comes in several flavors. Rapid-acting insulins (like lispro, aspart) start working in about 10–15 minutes, peak around 1 hour, and last 3–5 hours — they’re the ones you take right before meals. Short-acting (regular) begins around 30 minutes, peaks at 2–4 hours, and lasts up to 6–8 hours. Intermediate insulin (NPH) peaks 4–12 hours and can cover daytime or overnight needs. Long-acting basal insulins (glargine, detemir, degludec) provide steady coverage for 24 hours or more. Knowing which type you have tells you when to eat, check glucose, and expect effects.

If you use a basal-bolus plan, basal covers background needs and bolus covers meals. For pumps, rapid-acting insulin handles both basal and bolus needs in small, programmable doses.

Practical dosing and safety tips

Don’t guess doses. Your prescriber gives a starting plan based on weight, carbs, and blood sugar patterns. Carb counting helps: many people use a ratio (for example, 1 unit per 10–15 g of carbs) plus a correction dose for high glucose. Check blood sugar before dosing when possible — that reduces surprises.

Watch for low blood sugar (hypoglycemia). A reading under 70 mg/dL is low. Treat with 15 grams of fast carbs (3–4 glucose tablets, 4 oz fruit juice, or 1 tablespoon sugar). Recheck in 15 minutes and repeat if still low. Keep glucagon at home for severe lows where the person can’t swallow, and make sure family or caregivers know how to use it.

Rotate injection sites: use abdomen, thighs, buttocks, or upper arms, but move at least an inch each time. Reusing the same spot causes lipohypertrophy — lumps that change how insulin absorbs. Use short, single-use needles and dispose of them in a sharps container.

Mixing insulins: some regimens allow mixing NPH and short/regular in one syringe (NPH last), but many modern insulins shouldn’t be mixed. Check instructions or ask your provider.

Storage and travel: unopened insulin stays refrigerated. Once opened, most pen or vial insulins are OK at room temperature for 28 days (check the specific product). Avoid freezing and keep insulin out of direct heat. For travel, carry insulin in hand luggage with a cool pack — don’t put it in checked baggage.

If you’re starting or changing insulin, keep frequent glucose checks, write down doses and meals, and stay in touch with your care team. Small changes in timing, dose, or food can make a big difference.

Questions about mixing, timing, pumps, or travel? Reach out to your diabetes educator or clinician — they can help you fit insulin into your daily life safely.