Insulin Aspart Is a Rapid-Acting Insulin Used to Control Blood Sugar in People with Type 1 and Type 2 Diabetes

If you or someone you care about has been prescribed Insulin Analog, Aspart, you probably have questions. What exactly is it? How does it work? How much does it cost? This guide covers everything you need to know about Insulin Aspart in 2026, written in plain language.

What Is Insulin Aspart?

Insulin Aspart is a rapid-acting insulin analog — a lab-made version of the insulin your body naturally produces. It's designed to work faster than regular human insulin, making it ideal for controlling blood sugar spikes at mealtimes.

Brand Names and Manufacturers

• NovoLog — The original brand, made by Novo Nordisk. Available as FlexTouch pens (other formats discontinued in 2025).
• Fiasp — A faster-acting formulation of Insulin Aspart, also made by Novo Nordisk. Contains added niacinamide (vitamin B3) to speed absorption.
• Merilog (Insulin Aspart-szjj) — The first FDA-approved biosimilar to NovoLog, made by Sanofi. Approved February 2025.
• Kirsty (Insulin Aspart-xjhz) — The first interchangeable biosimilar to NovoLog, made by Biocon/Viatris. Approved July 2025. Can be substituted at the pharmacy without prescriber approval.

Drug Class

Insulin Aspart belongs to the rapid-acting insulin analog class. Other drugs in this class include Insulin Lispro (Humalog, Admelog, Lyumjev) and Insulin Glulisine (Apidra).

Controlled Substance Status

Insulin Aspart is not a controlled substance. It does not have a DEA schedule.

FDA Approval

NovoLog (Insulin Aspart) was approved by the FDA for the treatment of diabetes mellitus in adults and pediatric patients. Fiasp received approval as a faster-acting mealtime insulin option. Both biosimilars, Merilog and Kirsty, received FDA approval in 2025.

What Is Insulin Aspart Used For?

Insulin Aspart is FDA-approved for:

• Type 1 diabetes — In Type 1, the body produces little or no insulin. Insulin Aspart is used as mealtime (bolus) insulin alongside a long-acting insulin to maintain blood sugar control throughout the day.
• Type 2 diabetes — When oral medications and lifestyle changes aren't enough to control blood sugar, doctors may add Insulin Aspart to cover meals.
• Pediatric diabetes — Approved for children with both Type 1 and Type 2 diabetes.

Insulin Aspart is also used off-label for:

• Diabetic ketoacidosis (DKA) management in hospital settings
• Hyperkalemia treatment (given with glucose intravenously)
• Gestational diabetes when insulin therapy is required

How Is Insulin Aspart Taken?

Insulin Aspart is given as a subcutaneous injection (a shot under the skin) or through an insulin pump.

Injection Timing

• NovoLog: Inject 5-10 minutes before a meal
• Fiasp: Inject at the start of a meal, or within 20 minutes after starting a meal (it works even faster than NovoLog)

Where to Inject

Common injection sites include:

• Abdomen (fastest absorption)
• Front of the thigh
• Upper arm

Rotate injection sites within the same area to prevent lipodystrophy (skin changes from repeated injections in the same spot).

Dosage

Dosing is individualized based on your blood sugar levels, A1C, weight, diet, and physical activity. Some general guidelines:

• Starting dose: Total daily insulin is typically 0.2-0.6 units per kilogram of body weight per day
• Mealtime insulin (like Insulin Aspart) usually makes up 50-70% of total daily insulin
• Individual meal doses commonly range from 4-20 units, depending on carbohydrate intake
• Your doctor will adjust your dose based on blood sugar monitoring

Available Forms

• NovoLog FlexTouch prefilled pen (100 units/mL, 3 mL)
• Fiasp FlexTouch prefilled pen (100 units/mL, 3 mL)
• Fiasp vial (100 units/mL)
• Merilog and Kirsty biosimilars (available in pen and vial formats)
• Compatible with most insulin pumps for continuous subcutaneous infusion

Note: Novo Nordisk discontinued NovoLog 10 mL vials, PenFill cartridges, and FlexPens as of December 31, 2025. If you were using one of these formats, talk to your doctor about switching to the FlexTouch pen or a biosimilar.

Who Should Not Take Insulin Aspart?

Do not use Insulin Aspart if you:

• Are allergic to Insulin Aspart or any of its ingredients
• Are currently experiencing hypoglycemia (low blood sugar) — wait until your blood sugar is back in normal range

Use with caution if you have:

• Kidney or liver disease — These conditions slow insulin clearance and increase the risk of hypoglycemia. Your doctor may need to reduce your dose.
• Are taking thiazolidinediones (Pioglitazone, Rosiglitazone) — The combination increases risk of heart failure and fluid retention.

Tell your doctor about all medications, supplements, and health conditions before starting Insulin Aspart. For a complete list, see our guide on Insulin Aspart drug interactions.

How Much Does Insulin Aspart Cost?

Insulin affordability is a major concern — and the landscape has improved significantly in recent years. Here's what you can expect to pay in 2026:

Without Insurance

• Brand-name NovoLog/Fiasp: $130-$350 per box of 5 pens or per vial at retail pharmacy
• Authorized generic Insulin Aspart: $74-$100 per vial with discount cards
• Biosimilars (Merilog, Kirsty): Expected to be priced below brand-name NovoLog

With Insurance

• Medicare: Thanks to the Inflation Reduction Act, Medicare patients pay no more than $35 per month for insulin — all insulin products, including Insulin Aspart
• Commercial insurance: Copays vary by plan, but Novo Nordisk's Savings Card can reduce costs to as low as $25 per prescription

Savings Programs

• Novo Nordisk My$35 Program: Caps out-of-pocket costs at $35/month for eligible patients
• NovoCare Savings Card: Eligible commercially insured patients may pay as little as $25 per fill
• Patient Assistance Program: Uninsured or underinsured patients at or below 400% of the federal poverty level may qualify for free insulin through NovoCare

For a complete breakdown of savings options, see our guide on how to save money on Insulin Aspart.

What's New in 2026?

Several developments are shaping the Insulin Aspart landscape this year:

• Biosimilar competition: With Merilog and Kirsty now available, patients have more affordable options. Kirsty's interchangeable status means pharmacists can substitute it freely.
• Product discontinuations: Older NovoLog delivery formats are gone. If you're affected, talk to your doctor about transitioning to FlexTouch pens or biosimilars.
• Price reductions: Novo Nordisk cut list prices by up to 75% on several insulin products, including Fiasp, starting January 2026.
• Supply challenges: While improving, intermittent supply constraints persist. Use Medfinder to check pharmacy availability before making a trip.

Final Thoughts

Insulin Aspart is one of the most important medications in diabetes management. It's fast-acting, well-studied, and now more affordable than ever thanks to biosimilars and savings programs. Whether you're newly diagnosed or managing diabetes for years, understanding your medication puts you in control.

If you have questions about side effects, how Insulin Aspart works in your body, or finding a doctor who prescribes it, explore our other guides linked throughout this article.