Comprehensive medication guide to Insulin, Regular, Human including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$35/month maximum under Medicare Part D per the Inflation Reduction Act; most commercial plans cover Humulin R and Novolin R on Tier 1–2 with a $0–$35 copay. Manufacturer savings cards can further reduce commercial insurance out-of-pocket to $35/month.
Estimated Cash Pricing
$50–$100 retail for a 10 mL vial of Humulin R or Novolin R at most pharmacies; as low as $35/month with the Lilly Insulin Value Program or Novo Nordisk My Insulin Rx, no insurance required. Walmart ReliOn Novolin R is often the most affordable OTC option.
Medfinder Findability Score
72/100
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Insulin, Regular, Human — sold under the brand names Humulin R (Eli Lilly) and Novolin R (Novo Nordisk) — is a short-acting, synthetic human insulin used to lower blood glucose levels in people with diabetes mellitus. It is structurally identical to the insulin produced naturally by the human pancreas, created through recombinant DNA technology.
Unlike rapid-acting insulin analogs (such as Humalog or NovoLog), regular human insulin has a slower onset of action — approximately 30–60 minutes after subcutaneous injection. It is most commonly used as a mealtime insulin, administered 30 minutes before eating to control post-meal blood glucose spikes.
A unique and important feature of regular human insulin: the U-100 concentration is available over the counter at most U.S. pharmacies without a prescription. This makes it a critical safety net for uninsured patients and those in emergency situations.
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Regular human insulin works by binding to insulin receptors on the surface of skeletal muscle cells, fat cells, and liver cells. This binding activates a signaling cascade that moves glucose transport proteins (GLUT4) to the cell membrane, opening channels for glucose to enter from the bloodstream. The result is a fall in blood glucose levels as cells absorb and metabolize the sugar.
Simultaneously, insulin signals the liver to stop producing and releasing glucose (suppressing gluconeogenesis and glycogenolysis). It also promotes glycogen synthesis in the liver and muscle, and stimulates fat storage in adipose tissue. When injected subcutaneously, regular insulin forms hexamer clusters that must dissociate into monomers before absorption — this dissociation accounts for the 30–60 minute onset delay.
Regular insulin also activates the Na+/K+ ATPase pump, which moves potassium from the blood into cells — explaining its use (when given IV) to treat hyperkalemia, and its risk of causing hypokalemia as a side effect in high doses.
100 units/mL (U-100) — 10 mL multi-dose vial
Standard OTC vial — Humulin R (Lilly) and Novolin R (Novo Nordisk). Most common form.
100 units/mL (U-100) — 3 mL prefilled FlexPen
Novolin R FlexPen — OTC. Humulin R 3 mL vials permanently discontinued in 2024.
500 units/mL (U-500) — 3 mL KwikPen
Humulin R U-500 KwikPen — prescription only. For patients requiring very high insulin doses. U-500 vials discontinued late 2025.
100 units/100 mL (1 unit/mL) — IV infusion bag
Myxredlin — hospital use only. Premixed regular human insulin in 0.9% NaCl for IV administration.
Availability of regular human insulin in 2026 is generally good for most patients, though some formulations have been discontinued. Eli Lilly has permanently discontinued 3 mL Humulin R vials and U-500 vials. However, Humulin R 10 mL vials and all Novolin R presentations (10 mL vials and FlexPens) remain available. The U-100 formulations of both brands are sold OTC at major pharmacy chains nationwide.
Patients who previously used the discontinued 3 mL vials need to adapt to the 10 mL vial or switch to Novolin R. The main findability challenge is during this transition period, when some pharmacies may still be working through inventory changes or haven't yet updated their ordering.
If you're having trouble locating your specific insulin formulation, medfinder calls pharmacies near you to find which ones have your medication in stock and texts you the results.
Because regular human insulin is not a controlled substance, there are no DEA scheduling restrictions on who can prescribe it. Any licensed prescriber with authority to write prescriptions can order Humulin R or Novolin R. Additionally, the U-100 formulation is available OTC, meaning no prescription is required for the standard concentration.
Prescribers who commonly manage patients on regular insulin include:
Endocrinologists (preferred for Type 1 diabetes and complex regimens)
Primary care physicians (internists, family medicine) — manage most routine diabetes cases
Pediatricians and pediatric endocrinologists — for children with Type 1 or Type 2 diabetes
Obstetricians/gynecologists — for gestational diabetes management
Nurse practitioners (NPs) and physician assistants (PAs) — can prescribe in most U.S. states
Telehealth providers can also prescribe or renew regular insulin prescriptions via video or phone appointments, as there are no federal telehealth restrictions on non-controlled substances. This is particularly convenient for patients in rural areas or those requiring a prescription renewal between in-person visits.
No. Insulin, Regular, Human is not a DEA-scheduled controlled substance. It has no abuse potential classification, and there are no federal restrictions on who can prescribe it or how it can be dispensed. Any licensed prescriber — including primary care physicians, nurse practitioners, physician assistants, and specialists — can write a prescription for regular insulin.
Crucially, Humulin R U-100 and Novolin R U-100 are available over the counter at most U.S. pharmacies without any prescription at all. This OTC status is a unique and important safety feature for diabetic patients who may be in emergency situations, traveling, or between insurance coverage periods. The U-500 concentration of Humulin R, which is used for patients with severe insulin resistance requiring very high doses, does require a prescription.
The most important side effect is hypoglycemia (low blood sugar) — it is both the most common and the most potentially life-threatening. Other common side effects include:
Hypoglycemia: shakiness, sweating, rapid heartbeat, confusion, hunger, dizziness
Injection site reactions: redness, pain, swelling, itching
Weight gain
Edema (fluid retention)
Lipodystrophy (skin thickening or pitting at injection sites)
Serious side effects:
Severe hypoglycemia: seizures, unconsciousness, coma — medical emergency
Hypokalemia (low potassium): muscle weakness, cramps, abnormal heart rhythm
Severe allergic reaction/anaphylaxis: widespread rash, throat swelling, difficulty breathing — call 911
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Insulin Lispro (Humalog, Admelog)
Rapid-acting analog; onset 15 minutes vs 30–60 minutes for regular insulin. Injected right before meals. Generic insulin lispro available at ~$25/vial (Lilly). Requires prescription.
Insulin Aspart (NovoLog, Fiasp)
Rapid-acting analog; onset 10–20 minutes. Preferred for insulin pumps. Fiasp (faster aspart) is the fastest-acting formulation available. Requires prescription.
Insulin Glulisine (Apidra)
Rapid-acting analog with similar profile to lispro and aspart. Third rapid-acting option when others are unavailable or not tolerated. Requires prescription.
Novolin R (if on Humulin R)
Clinically equivalent to Humulin R at the same dose and concentration (U-100). Same active ingredient, different manufacturer (Novo Nordisk vs. Lilly). Available OTC. Most direct substitute.
Prefer Insulin, Regular, Human? We can find it.
Beta-blockers (metoprolol, atenolol, propranolol)
majorMask hypoglycemia symptoms (especially shakiness, rapid heartbeat) — sweating is the only symptom usually not masked. May prolong hypoglycemia by impairing glucose recovery.
Corticosteroids (prednisone, dexamethasone)
majorPromote insulin resistance and increase hepatic glucose production, raising blood sugar. May require 10–20% insulin dose increase. Doses must be reduced when steroids are tapered.
Sulfonylureas (glipizide, glimepiride, glyburide)
majorAdditive hypoglycemia risk when combined with insulin. Both classes lower blood sugar; concurrent use requires close monitoring and possible dose reduction.
Alcohol
majorImpairs liver's ability to counteract hypoglycemia (blocks gluconeogenesis); can mask hypoglycemia symptoms. Risk highest when drinking without food.
ACE inhibitors/ARBs (lisinopril, losartan)
moderateIncrease insulin sensitivity; may cause or worsen hypoglycemia, especially when starting or adjusting these medications.
Thiazide diuretics (hydrochlorothiazide, chlorthalidone)
moderateImpair insulin sensitivity and may reduce insulin effectiveness, raising blood glucose. Opposite effect to ACE inhibitors.
Atypical antipsychotics (olanzapine, clozapine, quetiapine)
moderateRaise blood glucose and cause weight gain, reducing insulin effectiveness. Increased monitoring required.
Fluoroquinolone antibiotics (ciprofloxacin, levofloxacin)
moderateUnpredictable effect on glycemia — can cause both hypoglycemia and hyperglycemia by altering insulin release from pancreatic beta cells.
Regular human insulin remains one of the most important medications in modern medicine. While newer rapid-acting analogs have largely replaced it in many clinical settings, regular insulin's OTC availability, established safety profile, and access through robust manufacturer savings programs make it an irreplaceable option — particularly for uninsured patients and those who have been stable on it for years.
The key supply changes to be aware of in 2026: the 3 mL Humulin R vial and U-500 vials are permanently discontinued. If your formulation has been affected, work with your prescriber to transition to the 10 mL Humulin R vial or Novolin R — both available OTC. Cost programs from Lilly and Novo Nordisk can cap your out-of-pocket to $35/month regardless of insurance.
If you need help locating your specific insulin formulation at a nearby pharmacy, medfinder calls pharmacies near you, finds which ones have your medication in stock, and texts you the results — saving you hours of hold-time phone calls.
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Our medication guides are researched and written to help patients make informed decisions. All content is reviewed for accuracy and updated regularly. Learn more about our standards
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