Fiasp FlexTouch is a disposable, prefilled insulin pen containing fast-acting insulin aspart formulated with niacinamide to speed absorption. It starts lowering blood glucose within about 2 to 3 minutes of injection, making it one of the fastest mealtime insulins available. Your doctor may prescribe it to help smooth out post-meal glucose peaks.
What Makes Fiasp “Ultra-Rapid”
Standard insulin aspart (sold as NovoLog/NovoRapid) begins working in 10 to 15 minutes. Fiasp’s formulation adds two excipients:
- Niacinamide (vitamin B3): increases the speed of absorption from the subcutaneous tissue.
- L-arginine: stabilizes the formulation.
The result is an insulin that starts lowering glucose in roughly 2 to 3 minutes, peaks around 1 to 3 hours, and has an overall duration of 3 to 5 hours. That head start matters because food starts raising glucose within minutes of the first bite.
The FlexTouch Pen at a Glance
FlexTouch is Novo Nordisk’s prefilled, disposable pen platform. The Fiasp version has these features:
- 300 units of U-100 insulin aspart per pen.
- Dose range of 1 to 80 units per injection, in 1-unit increments.
- Low push-force button with no extension as the dose increases.
- Audible click with each unit dialed and a final click when the dose is delivered.
- Designed for use with NovoFine or NovoTwist pen needles (sold separately).
Who Might Use Fiasp FlexTouch
Fiasp is FDA-approved for adults and children ages 1 and older with type 1 or type 2 diabetes who need mealtime insulin. It is typically used alongside a long-acting basal insulin as part of a basal-bolus regimen. People who tend to spike sharply after meals, who eat variably, or who want the option to dose after starting a meal sometimes prefer Fiasp over standard rapid-acting insulins. Final choice depends on cost, insurance coverage, and clinical response.
Injection Timing
The prescribing information recommends injecting Fiasp at the start of a meal, but allows administration up to 20 minutes after starting to eat. Many endocrinologists still favor pre-meal dosing for the smoothest post-meal glucose curve. Post-meal dosing is useful when:
- You are feeding a young child with unpredictable appetite.
- You are at a restaurant with an uncertain wait.
- You have gastroparesis and want to align insulin with actual food absorption.
Injection Technique Basics
- Wash your hands and inspect the pen. Fiasp should be clear and colorless; discard if cloudy or discolored.
- Attach a new pen needle and remove both caps.
- Prime the pen with 2 units, pointing the needle up, to clear air and confirm insulin flow.
- Dial your prescribed dose.
- Pinch a skin fold in the abdomen, thigh, upper arm, or buttock; insert the needle at 90 degrees.
- Press the button until the dose counter returns to 0; hold the needle in place for at least 6 seconds.
- Remove the needle, cap it safely, and dispose of it in an approved sharps container.
Rotate injection sites to reduce the risk of lipohypertrophy (lumpy fatty tissue that can cause erratic absorption).
Dosing and Adjustments
Your mealtime Fiasp dose is typically calculated from two numbers set by your care team: an insulin-to-carb ratio (units per gram of carbohydrate) and a correction factor (units per mg/dL above target). For example, with a 1:10 ratio and a 60-gram meal, you would take 6 units. Add a correction if your pre-meal glucose is above target.
Starting Fiasp from another rapid insulin often involves unit-for-unit conversion, but because absorption is faster, your team may fine-tune your carb ratio by 10 to 20 percent. For a broader look at insulin categories, see our treatment hub.
Storage Rules
| State | Storage | Use-By |
|---|---|---|
| Unused pens | Refrigerator, 36 to 46 deg F | Until expiration date on label |
| In-use pen | Room temperature, below 86 deg F | 28 days |
| Any pen, frozen | Do not use | Discard |
Never store insulin in a car on a hot day or next to a heating vent. Heat degrades insulin potency silently; glucose readings may rise before you notice anything wrong with the pen.
Common Side Effects
The most important potential side effect is hypoglycemia, or low blood sugar. Others reported in clinical trials and postmarketing data include:
- Injection-site reactions: redness, itching, or a small bruise.
- Lipodystrophy with repeated injections in the same spot.
- Weight gain (common with insulin in general).
- Allergic reactions (rare; contact your clinician for rash, swelling, or difficulty breathing).
- Hypokalemia, particularly if you have kidney disease or take certain diuretics.
According to the FDA prescribing information, severe hypoglycemia and hypokalemia are the most serious warnings.
Fiasp Versus Other Mealtime Insulins
| Insulin | Onset | Peak | Duration |
|---|---|---|---|
| Fiasp (aspart + niacinamide) | 2 to 3 min | 1 to 3 hr | 3 to 5 hr |
| Lyumjev (lispro-aabc) | 1 to 3 min | 1 to 3 hr | 3 to 5 hr |
| NovoLog / Humalog (standard rapid) | 10 to 15 min | 1 to 2 hr | 3 to 5 hr |
| Regular (Humulin R, Novolin R) | 30 min | 2 to 4 hr | 6 to 8 hr |
Using Fiasp in a Pump
Fiasp is FDA-approved for continuous subcutaneous insulin infusion. Some pump users note more site irritation or earlier infusion-set failures with Fiasp compared to standard aspart. If you switch, change sets every 2 days at first, monitor for redness, and discuss with your pump trainer. Not all pump algorithms are validated with Fiasp, so check with your pump manufacturer.
Cost and Coverage
Fiasp is typically priced similarly to other brand-name rapid-acting insulins. Manufacturer savings cards, patient assistance programs, and state copay-cap laws may reduce out-of-pocket costs. For Medicare beneficiaries, the Inflation Reduction Act caps monthly insulin copays. Call your pharmacy ahead of time to confirm pricing before filling.
When to Call Your Care Team
Reach out if you experience recurrent lows after switching to Fiasp, persistently high post-meal glucose despite correct carb counting, site reactions that do not resolve, or any signs of allergy. A timing or dose adjustment often solves the problem; occasionally, Fiasp is not the right fit and a switch back to standard aspart makes sense.
The Bottom Line
Fiasp FlexTouch is a convenient, ultra-rapid mealtime insulin pen that starts working within minutes and can be dosed at the start of a meal or up to 20 minutes after eating. It can help smooth post-meal glucose peaks and offers real-world flexibility, but hypoglycemia risk, storage rules, and individualized dosing still apply. Any insulin change should be coordinated with your diabetes care team.
