Alternatives to Merilog if You Can't Fill Your Prescription

If your pharmacy is out of Merilog (insulin aspart-szjj) and you need a rapid-acting insulin now, you have options. Several other medications work in the same way, and your doctor can help you switch safely.

In this guide, we'll cover what Merilog is, how it works, and the best alternatives available in 2026 — so you can make an informed decision with your healthcare team.

What Is Merilog?

Merilog is a rapid-acting insulin biosimilar made by Sanofi. It was FDA-approved on February 14, 2025, as the first biosimilar to NovoLog (insulin aspart). It's prescribed for adults and children with type 1 or type 2 diabetes to help control blood sugar around meals.

Merilog is available as a 10 mL vial and a 3 mL SoloStar prefilled pen, both containing 100 units/mL of insulin aspart-szjj. Through Sanofi's savings program, it's available for $35 or less per 30-day supply.

How Does Merilog Work?

Like all rapid-acting insulins, Merilog works by mimicking the insulin your pancreas would normally produce in response to eating. You inject it 5 to 10 minutes before a meal, and it:

• Helps your cells absorb glucose from the blood
• Prevents your liver from releasing too much glucose
• Starts working within 10 to 20 minutes
• Peaks between 1 and 3 hours after injection
• Lasts for 3 to 5 hours

It's typically used alongside a longer-acting basal insulin (like Lantus or Toujeo) to provide full 24-hour blood sugar coverage. For more detail, see our guide on how Merilog works.

Merilog Alternatives: Rapid-Acting Insulins

All of the alternatives below are in the same drug class — rapid-acting insulin analogs. They work similarly to Merilog and are injected before meals. However, they have different active ingredients, manufacturers, and pricing structures.

Always talk to your doctor before switching insulins. Even though these medications are similar, switching requires a prescription change and may involve dosing adjustments.

1. NovoLog (Insulin Aspart)

NovoLog is the reference product that Merilog was designed to match. Made by Novo Nordisk, it contains the same active ingredient — insulin aspart — and has been on the market since 2000.

• Active ingredient: Insulin aspart
• Available forms: 10 mL vial, FlexPen (3 mL prefilled pen)
• Approximate cash price: ~$72 per vial, ~$140 per FlexPen carton (5 pens) after Novo Nordisk's 2024 price reduction
• Key difference from Merilog: Essentially the same medication. Merilog is biosimilar to NovoLog, so they're clinically equivalent.

NovoLog is widely available and well-established, making it the most straightforward alternative if Merilog is out of stock.

2. Humalog (Insulin Lispro)

Humalog is a rapid-acting insulin made by Eli Lilly. It uses a different molecule — insulin lispro — but has a very similar onset, peak, and duration compared to insulin aspart.

• Active ingredient: Insulin lispro
• Available forms: 10 mL vial, KwikPen (3 mL prefilled pen), Humalog Tempo Pen
• Approximate cash price: ~$35 per vial (after Lilly's 2023 price reduction), ~$80-$100 per KwikPen carton
• Key difference from Merilog: Different active ingredient but same drug class. Slightly different molecular structure, though clinical outcomes are comparable for most patients.

Humalog is one of the most widely prescribed rapid-acting insulins in the U.S. and is easy to find at most pharmacies.

3. Admelog (Insulin Lispro)

Admelog is a biosimilar to Humalog, also made by Sanofi — the same company that makes Merilog. If you're already comfortable with Sanofi products and the SoloStar pen delivery system, Admelog may feel familiar.

• Active ingredient: Insulin lispro
• Available forms: 10 mL vial, SoloStar prefilled pen (3 mL)
• Approximate cash price: $35 per 30-day supply through Sanofi's Insulins Valyou Savings Program
• Key difference from Merilog: Contains insulin lispro instead of insulin aspart. Uses the same SoloStar pen device, so the injection experience is identical.

Because Admelog is covered under the same Sanofi Insulins Valyou Savings Program, you can get it for $35/month — the same price as Merilog.

4. Apidra (Insulin Glulisine)

Apidra is another rapid-acting insulin from Sanofi, using a third type of insulin analog — insulin glulisine.

• Active ingredient: Insulin glulisine
• Available forms: 10 mL vial, SoloStar prefilled pen (3 mL)
• Approximate cash price: $35 per 30-day supply through Sanofi's savings program
• Key difference from Merilog: Different molecule with a slightly faster onset in some studies. Less widely prescribed than insulin aspart or lispro, but effective for many patients.

5. Fiasp (Insulin Aspart)

Fiasp is an ultra-rapid-acting formulation of insulin aspart made by Novo Nordisk. It contains the same active ingredient as Merilog and NovoLog but includes niacinamide to speed up absorption.

• Active ingredient: Insulin aspart (with added niacinamide)
• Available forms: 10 mL vial, FlexTouch prefilled pen (3 mL)
• Approximate cash price: ~$150-$200 without coupons
• Key difference from Merilog: Faster onset than standard insulin aspart. However, Fiasp FlexTouch pens have been in shortage through early 2026, so availability may be limited.

Note: Due to ongoing supply issues with Fiasp, it may not be the most reliable backup option right now.

How to Talk to Your Doctor About Switching

If you can't find Merilog and need to switch to an alternative, here's what to bring up with your doctor:

• Which alternative makes the most sense for your diabetes type and current regimen
• Whether dosing needs to change (in most cases, the dose is equivalent, but your doctor will confirm)
• Pen vs. vial preference — if you're used to the SoloStar pen, Admelog and Apidra use the same device
• Insurance coverage — some alternatives may be better covered on your plan
• Cost considerations — savings programs vary by manufacturer

Final Thoughts

Running out of options for Merilog doesn't mean running out of options for managing your diabetes. NovoLog, Humalog, Admelog, Apidra, and Fiasp all provide rapid-acting insulin coverage — and your doctor can help you find the one that's right for your situation.

In the meantime, keep checking Medfinder for Merilog availability in your area. Supply is expected to improve as 2026 progresses, and you may be able to switch back once Merilog is consistently in stock.

For more on Merilog, read our guides on what Merilog is and Merilog side effects.