Merilog Shortage: What Providers and Prescribers Need to Know in 2026

Merilog (insulin aspart-szjj) — the first FDA-approved rapid-acting insulin biosimilar — has become an important option in diabetes management since its launch. However, providers across the country are fielding patient complaints about difficulty filling Merilog prescriptions.

This briefing covers the current availability picture, key prescribing considerations, and practical resources to help your patients access their medication.

Timeline: Merilog's Path to Market

• February 14, 2025: FDA approves Merilog (insulin aspart-szjj) as the first biosimilar to NovoLog (insulin aspart) for glycemic control in adults and pediatric patients with diabetes mellitus.
• July 2025: Merilog becomes commercially available in U.S. pharmacies. Available as 10 mL vials and 3 mL SoloStar prefilled pens (100 units/mL).
• September 2025: Sanofi announces expansion of its Insulins Valyou Savings Program to cover all Sanofi insulins at $35/month.
• December 31, 2025: Novo Nordisk discontinues its unbranded insulin aspart (authorized generic of NovoLog), reducing available rapid-acting insulin supply sources.
• January 1, 2026: Sanofi's expanded $35/month insulin pricing takes effect for all patients regardless of insurance status.
• Early 2026: Ongoing Fiasp FlexTouch pen shortages continue, pushing additional demand toward Merilog and other rapid-acting insulins.

Prescribing Implications

Clinical Equivalence

Merilog is biosimilar to NovoLog — not interchangeable. While clinical data demonstrates equivalent efficacy and safety, pharmacists cannot automatically substitute Merilog for NovoLog without a new prescription. If you're switching a patient from NovoLog to Merilog, a new prescription is required.

Key clinical parameters:

• Onset: 10-20 minutes (comparable to NovoLog)
• Peak effect: 1-3 hours post-injection
• Duration: 3-5 hours
• Dosing: Inject subcutaneously 5-10 minutes before meals, used with intermediate- or long-acting basal insulin
• Do not mix with any other insulin products

Contraindications and Warnings

Standard insulin aspart contraindications apply:

• Contraindicated during episodes of hypoglycemia
• Contraindicated in patients with hypersensitivity to insulin aspart or excipients
• No boxed warning
• Monitor for hypokalemia, especially in patients on potassium-lowering agents
• Caution with concomitant thiazolidinedione (TZD) use — risk of fluid retention and heart failure exacerbation

For complete prescribing details, see our clinical overview of Merilog drug interactions.

Special Populations

• Pediatric: Approved for pediatric patients; studied in patients ages 2-18 with type 1 diabetes
• Pregnancy: No evidence of adverse fetal effects; monitor glucose closely as insulin requirements may change
• Renal/hepatic impairment: Increased hypoglycemia risk; more frequent glucose monitoring and potential dose adjustment needed
• Geriatric: No dose adjustment needed, but closely monitor due to polypharmacy considerations

Current Availability Picture

As of early 2026, Merilog is not listed on the FDA or ASHP shortage databases. However, real-world availability is inconsistent due to:

• Distribution ramp-up: As a product less than a year old, wholesale and retail distribution channels are still maturing
• Formulary lag: Many PBMs and insurance plans have not yet added Merilog to their formularies, reducing pharmacy incentive to stock it
• Market disruption: The discontinuation of Novo Nordisk's unbranded insulin aspart and ongoing Fiasp shortages have created unexpected demand surges

Providers should expect availability to improve progressively through 2026 as formulary adoption accelerates.

Cost and Access Considerations

Merilog offers strong cost advantages for patients:

• Sanofi Insulins Valyou Savings Program: $35 per 30-day supply for all patients (insured or uninsured)
• Sanofi Copay Savings: Commercially insured patients pay no more than $35/month
• Medicare Part D: $35/month cap under the Inflation Reduction Act
• Sanofi Patient Connection: Free medication for eligible patients meeting financial need criteria (apply at sanofipatientconnection.com)

These programs make Merilog one of the most affordable rapid-acting insulin options on the market. For uninsured patients, the $35 Valyou program is particularly valuable. More details in our provider's guide to helping patients save on Merilog.

Tools and Resources for Providers

Medfinder for Providers

Medfinder offers a provider-facing tool that helps locate pharmacies with Merilog in stock. You can direct patients to check availability in real time, or your staff can search on their behalf during the visit.

Therapeutic Alternatives

When Merilog is unavailable, consider these clinically comparable alternatives:

• NovoLog (insulin aspart): The reference product — same active ingredient, widely available
• Humalog (insulin lispro): Different molecule, equivalent clinical profile, available at ~$35/vial after Eli Lilly's price reduction
• Admelog (insulin lispro): Sanofi-manufactured biosimilar to Humalog — covered under the same $35/month Valyou program
• Apidra (insulin glulisine): Another Sanofi rapid-acting insulin — also $35/month through Valyou

For a comprehensive comparison, see alternatives to Merilog.

Prescribing Tips for Availability

1. Write "dispense as written" only when clinically necessary. Flexibility in insulin selection improves the odds of the pharmacy having stock.
2. Consider prescribing both vial and pen options. Vials may be more available than pens (or vice versa) at different pharmacies.
3. Alert patients to the Valyou Savings Program. Many patients don't know about Sanofi's $35/month offer — a quick mention can eliminate cost barriers.
4. Use e-prescribing to enable pharmacy sourcing. When you send the prescription electronically, the pharmacy can begin sourcing before the patient arrives.

Looking Ahead

Merilog's entry represents a meaningful shift in the rapid-acting insulin market. As the first insulin aspart biosimilar, it increases competitive pressure on pricing and supply. Additional insulin biosimilars are expected to receive FDA approval in the coming years, further expanding patient options.

For now, the combination of Sanofi's aggressive pricing ($35/month for all patients) and expanding distribution makes Merilog a strong choice for newly initiating patients and those switching from other rapid-acting insulins — provided pharmacy access continues to improve.

Final Thoughts

Merilog is clinically equivalent to NovoLog, significantly more affordable, and backed by robust patient access programs. The availability challenges are real but improving. As a prescriber, you can help your patients by staying informed about the supply landscape, using tools like Medfinder to locate stock, and being prepared with alternative prescribing strategies when needed.

For more provider resources, see our guide on how to help patients find Merilog in stock.