Novolin R is regular human insulin manufactured by Novo Nordisk — a short-acting insulin with onset of 30 minutes, peak at 2 to 4 hours, and duration of 5 to 8 hours. It is the same molecule as Humulin R with the same clinical effects. Walmart sells a Novolin R version branded ReliOn over the counter for about $25 per vial, making it one of the most affordable insulins available in the United States. It is injected 30 minutes before meals. Dose and timing should be individualized with a prescriber.
What Novolin R Is
Novolin R is the brand name for regular human insulin from Novo Nordisk. It is biosynthetic human insulin produced by recombinant DNA technology — identical in structure to the insulin naturally produced by the human pancreas. The “R” denotes “regular,” meaning standard short-acting insulin without protamine modification.
Novolin R is supplied as:
- 10 mL U-100 vials (sold in pharmacies)
- ReliOn Novolin R 10 mL vials (sold at Walmart pharmacies, often without prescription in most states)
It is functionally and pharmacologically equivalent to Humulin R (manufactured by Eli Lilly). The two products are interchangeable in most clinical situations.
How Novolin R Works
Regular insulin in solution exists primarily as hexamers — clusters of six insulin molecules held together by zinc ions. Before absorption into the bloodstream, hexamers must dissociate into dimers and then monomers. This dissociation process is the rate-limiting step for absorption from subcutaneous tissue.
Once in the bloodstream, regular insulin binds insulin receptors on liver, muscle, and fat cells with the same affinity as native human insulin, lowering blood glucose by suppressing liver glucose output and increasing glucose uptake by peripheral tissues.
Pharmacokinetics: Onset, Peak, Duration
| Parameter | Novolin R (regular insulin) |
|---|---|
| Onset of action | 30 minutes |
| Peak effect | 2 to 4 hours |
| Duration of action | 5 to 8 hours |
| Recommended timing | 30 minutes before a meal |
| Concentration | U-100 (100 units/mL) |
| Appearance | Clear and colorless solution |
Who Novolin R Is For
- Adults with type 1 or type 2 diabetes who need mealtime insulin and want a lower-cost option
- Cost-sensitive patients without insurance or with limited prescription coverage
- Hospitalized patients on subcutaneous sliding-scale protocols
- Patients requiring a stopgap supply (Walmart OTC access between prescriber visits)
- Patients using older-generation diabetes care plans designed around regular insulin
Novolin R Walmart OTC Access
Novolin R sold as ReliOn at Walmart pharmacies is available over the counter in most US states for about $25 per 10 mL U-100 vial. The OTC status is a longstanding regulatory exception that predates modern prescription drug regulations for insulin. Practical implications:
- No prescription is required in most states to purchase Novolin R at Walmart
- Mississippi, Indiana, and a few other states have specific state-level prescription requirements that may apply
- OTC insulin access is a critical safety net for uninsured or under-insured patients
- OTC does not mean safe to use without medical guidance — hypoglycemia, DKA, and dosing errors remain real risks
- People relying on OTC insulin should still seek diabetes care for prescription-strength glucose monitoring, A1C testing, and complication screening
How Novolin R Is Used
- Inject subcutaneously into the abdomen, thigh, upper arm, or buttock using a U-100 syringe
- Inject 30 minutes before a meal to allow time for onset of action
- Calculate dose based on prescriber-set insulin-to-carb ratio plus correction factor, or follow a sliding scale
- Pair with a long-acting basal insulin (Lantus, Tresiba, Toujeo, NPH) for type 1 diabetes coverage
- Site rotation reduces lipohypertrophy
Novolin R vs Other Mealtime Insulins
| Insulin | Onset | Peak | Duration | Approximate Cost per Vial |
|---|---|---|---|---|
| Novolin R (Walmart ReliOn) | 30 min | 2 to 4 hr | 5 to 8 hr | $25 |
| Humulin R | 30 min | 2 to 4 hr | 5 to 8 hr | $25 to $50 |
| Novolog (aspart) | 5 to 15 min | 30 to 90 min | 3 to 5 hr | $100 to $150 |
| Humalog (lispro) | 5 to 15 min | 30 to 90 min | 3 to 5 hr | $100 to $150 |
| Apidra (glulisine) | 10 to 15 min | 60 to 90 min | 3 to 4 hr | $100 to $150 |
Trade-offs of Choosing Regular Insulin
Advantages
- Much lower cost ($25 vial vs $100+ for rapid analogs)
- Walmart OTC availability without prescription in most states
- Long safety record (since the 1980s)
- Suitable for hospital sliding scales and IV use
- Available for pregnant patients with extensive safety data
Disadvantages
- Requires 30-minute pre-meal injection — inconvenient and easy to forget
- Higher rate of late post-meal hypoglycemia (3 to 4 hours after eating)
- Worse postprandial glucose control than rapid-acting analogs
- Less flexibility for meal timing variability
- Higher A1C in some head-to-head trials compared with rapid analogs
Side Effects
- Hypoglycemia — most common side effect, especially if meal is delayed or skipped after injection
- Weight gain — typical of intensified insulin therapy
- Injection site reactions — redness, itching, small lumps
- Lipodystrophy (lipohypertrophy or lipoatrophy) from repeated injections in the same spot
- Allergic reactions — local or rare anaphylaxis
- Hypokalemia (low potassium) — uncommon
- Peripheral edema, especially with thiazolidinediones
Storage and Handling
- Unopened vials: refrigerate at 36 to 46 °F (2 to 8 °C)
- In use: room temperature up to 77 °F (25 °C) for up to 42 days, then discard
- Do not freeze; do not expose to direct heat or sunlight
- Solution is clear and colorless — discard if cloudy, discolored, or contains particles
- Do not share vials between people
Sliding Scale Insulin
Many sliding-scale insulin protocols use regular insulin (Novolin R or Humulin R) because of its slower onset and longer duration, which provide a smoother fall in glucose over several hours. Sliding scales are typically:
- Pre-meal glucose 150 to 200 mg/dL: 2 units
- Pre-meal glucose 201 to 250 mg/dL: 4 units
- Pre-meal glucose 251 to 300 mg/dL: 6 units
- Continuing scale at higher glucose levels per prescriber instructions
Sliding scales are largely reactive — they correct hyperglycemia rather than preventing it. Modern outpatient diabetes care emphasizes carbohydrate counting and basal-bolus insulin instead, though sliding scales remain common in hospitals and for some long-term care settings.
Practical Tips
- Set a timer for 30 minutes after injection to align with meal start
- If your meal is delayed, delay the injection
- Keep glucose tablets or juice nearby — the 2 to 4 hour peak can cause late lows if you eat less than planned
- If switching from rapid analog to Novolin R, expect higher post-meal readings and adjust timing
- Use the OTC Walmart access for emergencies, not as a long-term substitute for diabetes care
Cost and Access
- Walmart ReliOn Novolin R: about $25 per 10 mL U-100 vial, often without prescription
- Other pharmacy Novolin R: about $50 to $100 per vial without insurance
- Medicare Part D covers Novolin R at the federal $35 monthly cap
- Novo Nordisk patient assistance programs available
- Most commercial insurance plans cover Novolin R, often as the preferred regular insulin
Related Reading
For broader context, see our overview of diabetes treatment, the comparison guide on Humulin R, and our page on insulin sliding scale protocols.
The Bottom Line
Novolin R is regular human insulin from Novo Nordisk — short-acting, with onset in 30 minutes, peak at 2 to 4 hours, and duration of 5 to 8 hours. It is injected 30 minutes before meals and is pharmacologically identical to Humulin R. Walmart sells it as ReliOn for about $25 per vial over the counter in most states, making it one of the most affordable insulins available. The trade-off is worse mealtime glucose control and more late post-meal lows than rapid-acting analogs. Side effects include hypoglycemia, weight gain, and injection site reactions. OTC availability is a critical safety net but does not replace medical guidance — talk to a prescriber to set dosing and monitor glucose safely.
