What Is Insulin, Regular, Human? Uses, Dosage, and What You Need to Know in 2026

Regular human insulin is one of the oldest and most important medications in modern medicine. Despite the rise of newer, faster-acting insulin analogs, regular insulin remains widely used — particularly by patients who depend on its OTC availability and its effectiveness in both Type 1 and Type 2 diabetes. Here's a plain-English guide to everything you need to know.

What Is Regular Human Insulin?

Regular human insulin is a synthetic, man-made version of the insulin your pancreas produces naturally. It's called "human" insulin because its structure is identical to natural human insulin — unlike older animal-derived insulins derived from pigs or cattle.

It is classified as a short-acting insulin, meaning it begins working within 30–60 minutes of injection, reaches its peak effect at 2–3 hours, and lasts about 5–8 hours. This distinguishes it from:

Rapid-acting analogs (e.g., Humalog, NovoLog): work in 10–15 minutes, inject right before meals

Intermediate-acting insulin (NPH, Humulin N): works over 12–16 hours, used for background (basal) coverage

Long-acting analogs (Lantus, Toujeo, Levemir): work over 20–24 hours, once-daily basal dosing

Brand Names and Forms

Regular human insulin is sold under these brand names in the U.S.:

Humulin R (Eli Lilly) — U-100 (10 mL vial) and U-500 KwikPen (prescription only)

Novolin R (Novo Nordisk) — U-100 (10 mL vial and FlexPen); also sold as ReliOn Novolin R at Walmart

Myxredlin — Premixed IV formulation (100 units/mL in 0.9% NaCl), used only in hospital settings

Important: Humulin R U-100 and Novolin R U-100 are available over the counter at most U.S. pharmacies without a prescription. The U-500 formulation requires a prescription.

What Is Regular Human Insulin Used For?

The FDA has approved regular human insulin to improve blood sugar control in adults and children with:

Type 1 diabetes mellitus — The pancreas produces little or no insulin; insulin must be replaced

Type 2 diabetes mellitus — When diet, exercise, and oral medications no longer control blood sugar adequately

Off-label uses include: gestational diabetes (in some cases), diabetic ketoacidosis (DKA) when given IV, and hyperkalemia (high potassium) treatment via IV insulin + dextrose in hospital settings.

How Is Regular Insulin Taken?

Subcutaneous injection: Inject under the skin of the abdomen, thigh, upper arm, or buttocks, approximately 30 minutes before a meal. Rotate injection sites to prevent lipodystrophy.

Intravenous (IV): Only under medical supervision in hospital settings. Do NOT inject regular insulin intravenously at home.

Insulin pumps: Generally not recommended with regular human insulin (Novolin R specifically states not to use in pumps due to precipitation risk). Rapid-acting analogs are the preferred choice for insulin pumps.

Dosing: How Much Do You Take?

Dosing is highly individualized and must be determined by your prescriber based on blood glucose goals, carbohydrate intake, weight, activity level, and other medications. There is no single "standard" dose.

A common starting point for Type 2 diabetes newly requiring insulin: 10 units per day (or 0.1–0.2 units/kg/day), taken in the evening or split twice daily. For Type 1 diabetes, the regimen is more complex and involves both mealtime insulin (like regular insulin) and a basal insulin.

How to Store Regular Human Insulin

Unopened: Refrigerate at 36–46°F until expiration date

Opened Humulin R vials: Room temperature for up to 28 days

Opened Novolin R vials: Room temperature for up to 42 days

Never freeze insulin or expose it to extreme heat above 98.6°F (37°C)

Learn more about how regular insulin works at the molecular level: How Does Insulin, Regular, Human Work? Mechanism of Action Explained.

Having trouble finding regular insulin at your pharmacy? medfinder calls nearby pharmacies for you and texts you which ones can fill your prescription.