Regular Insulin (Humulin R, Novolin R): Timing & Cost
Regular human insulin explained: why it is taken 30 minutes before meals, over-the-counter U-100 vs prescription U-500, safety and low-cost options.
3 min read
Key takeaways
Regular insulin is short-acting human insulin taken about 30 minutes before a meal. U-100 Humulin R and Novolin R are sold over the counter at many US pharmacies and are among the cheapest insulins; concentrated Humulin R U-500 needs a prescription.
Regular insulin at a glance
| Generic name | human insulin (regular) |
|---|---|
| Made by | Eli Lilly; Novo Nordisk |
| Type | Short-acting insulin |
| Form | Vials, pens |
| How often | Before meals |
| United States | FDA-approved. U-100 is sold over the counter at many US pharmacies; Humulin R U-500 requires a prescription. |
| Canada | Available in Canada. |
Full Regular insulin reference: uses, dosing, side effects →
How it differs from rapid-acting insulin
Regular insulin starts more slowly and lasts longer than lispro or aspart. That is why it is injected about half an hour before eating, and why lows can happen several hours after a meal.
Over the counter — but not without guidance
Being able to buy U-100 regular insulin without a prescription helps in a pinch, but switching from a modern insulin is not unit-for-unit simple. Talk to a clinician or pharmacist before you change, even for a short time.
U-500: a different product
Humulin R U-500 is five times more concentrated. It is prescribed for people who need very large doses and uses its own dedicated pen or syringe. Mix-ups between U-100 and U-500 can cause dangerous lows.
Low blood sugar
Know your low-sugar plan. Signs include shaking, sweating, a fast heartbeat, hunger, confusion and irritability. A common approach is the rule of 15: take 15 g of fast-acting carbohydrate (glucose tablets, juice or regular soda), recheck after 15 minutes, and repeat if still low. Make sure someone close to you knows how to use rescue glucagon.
Storage
Unopened: refrigerate. In use: follow the product labeling, often 31–42 days.
Frequently asked questions
Can I inject regular insulin right before eating?
It works best about 30 minutes before a meal. Ask your clinician how to adjust if that is hard to fit into your routine.
Is store-brand insulin the same?
Store-brand human insulins are the same regular or NPH insulin sold under a pharmacy brand.
Is regular insulin used in emergencies?
Hospitals use it intravenously; at home it is a mealtime insulin.
Keep reading
Sources
Checked against these primary sources on .
General information based on the official label. It does not replace advice from your prescriber or pharmacist.