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Insulin aspart (NovoLog / NovoRapid)

Novo Nordisk

The long-standing rapid-acting mealtime analog and the practical reference point for "rapid insulin": approved since 1999–2000, pump-cleared, available almost everywhere (now with biosimilars) — but slower than a healthy pancreas and the baseline the ultra-rapid formulations were built to beat.

Available nowRegulator-approvedrapidmealtime

The scorecard

Onset speed58

Rapid-peer convention. Onset of action ~25 min and onset of appearance ~7 min in clamp studies — reliable, but the baseline ultra-rapid analogs improve on.[3]

Time to peak55

Rapid-peer convention (faster peak = better for mealtime). Median plasma Tmax 40–50 min; peak glucose-lowering effect 1–3 h — the familiar mealtime lag people pre-bolus around.[1]

Short tail55

Rapid-peer convention (short = better for mealtime). 3–5 h duration, ~81-min half-life; a typical rapid-analog tail with normal stacking risk.[1]

Consistency70

Decades of clamp and trial data; well characterized, though absorption still varies with injection site, blood flow, and activity.[1]

Exercise flexibility52

Standard rapid-analog behavior; the 3–5 h tail means pre-meal doses are typically halved before activity to avoid lows.[7]

Access & cost80

Among the most widely available analogs across all major regions, now with FDA-approved biosimilars (the first interchangeable rapid-acting insulin) lowering cost.[8]

Insulins are scored relative to their role peers (see tags: rapid, ultra-rapid, basal, inhaled). A basal insulin's onset score compares it to other basals, not to mealtime insulins.

Editor’s take

The honest baseline. It's the insulin most loops were tuned on and the one ultra-rapid analogs are measured against — a useful zero-point for the speed rankings rather than a leader on them. "Good, available, and increasingly affordable" is itself worth a lot.

The full picture

Insulin aspart is the workhorse rapid-acting mealtime analog — the one that defined "mealtime insulin" for a generation. It's made by Novo Nordisk under the brand names NovoLog (US) and NovoRapid (rest of world), approved in the EU in September 1999 and in the US around 2000.12 A single amino-acid swap (proline → aspartic acid at position B28) discourages the molecule from clumping into hexamers, so after a subcutaneous injection it breaks apart and is absorbed faster than older "regular" human insulin.3

Type and role. This is a rapid (mealtime/bolus) insulin — taken to cover the carbohydrate in a meal, not to provide background coverage. It is scored here against other rapid analogs, so its numbers are the genre's reference point rather than a basal-style flat curve.

PK/PD — the real numbers. Injected under the skin it begins working within roughly 10–20 minutes; in clamp studies onset of action is around 25 minutes and the insulin first appears in the blood at about 7 minutes.4 Plasma levels peak at a median of 40–50 minutes — about twice as fast as regular human insulin (80–120 minutes) — while the maximum glucose-lowering effect lands 1–3 hours after the dose.5 Total duration is 3–5 hours, with an apparent half-life of about 81 minutes.5 Absolute bioavailability is roughly 80% (figure from faster-aspart PK data).6 The practical takeaway: even a "rapid" analog still lags a healthy pancreas, which is why post-meal spikes and the need to pre-bolus persist.7

Absorption variability. Onset and rate of absorption shift with the injection site, blood flow, temperature, and physical activity — the same dose can behave differently day to day.8 Across head-to-head trials, mealtime aspart lowers post-meal glucose more than regular insulin (about −22 mg/dL in type 1 diabetes) and modestly improves HbA1c with less late and nocturnal hypoglycemia.97

Exercise. Because the 3–5 hour tail keeps working during activity, circulating aspart is a leading cause of exercise lows; consensus guidance is to cut the pre-exercise meal bolus by roughly 50% (and/or add carbohydrate) for moderate activity.10

Delivery and approvals. Aspart is delivered by pen, syringe, insulin pump (it is cleared for continuous subcutaneous infusion), and intravenously in clinical settings.11 It is approved for type 1 and type 2 diabetes in adults and children — from age 1 in the EU.1

Access, cost, biosimilars. Aspart is among the most widely available analogs, sold across the US, UK, EU, Canada, Australia, and Japan. Lower-cost biosimilars have now arrived: the FDA approved Merilog (insulin aspart-szjj) in February 2025 as the first US aspart biosimilar, and Kirsty (insulin aspart-xjhz) followed as the first interchangeable rapid-acting insulin — meaning a pharmacist can substitute it for NovoLog.12

What's coming. The aspart molecule itself is mature; the frontier is making it faster. Novo Nordisk's faster aspart (Fiasp) adds niacinamide and L-arginine to roughly double early absorption, and newer ultra-rapid formulations push onset earlier still — all aimed at closing the gap between injected insulin and the body's own near-instant response.7 We therefore rank aspart as the reference point, not the frontrunner, on speed: it's the right zero-line for reading the insulin-speed gap, even as its access score climbs with biosimilar competition.

References

  1. European Medicines Agency. NovoRapid (insulin aspart) — European Public Assessment Report. EMA (authorised 1999). https://www.ema.europa.eu/en/medicines/human/EPAR/novorapid ↩ ↩2

  2. FDA / Novo Nordisk. NOVOLOG (insulin aspart) injection — prescribing information ("Initial U.S. Approval: 2000"). DailyMed (2000). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 ↩

  3. FDA / Novo Nordisk. NOVOLOG prescribing information — Clinical Pharmacology (B28 proline→aspartic-acid substitution reduces hexamer formation). DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 ↩

  4. Shiramoto M, et al. Fast-acting insulin aspart in Japanese patients with type 1 diabetes: faster onset… relative to insulin aspart. J Diabetes Investig (2017). PMID 28556616. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835461/ ↩

  5. FDA / Novo Nordisk. NOVOLOG prescribing information — median Tmax 40–50 min vs 80–120 min for regular human insulin; peak effect 1–3 h; duration 3–5 h; half-life ~81 min. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 ↩ ↩2

  6. Hövelmann U, et al. Pharmacokinetic properties of fast-acting insulin aspart in different subcutaneous injection regions (absolute bioavailability ~80%; figure measured for faster aspart / Fiasp, not conventional insulin aspart). Clin Drug Investig (2017). PMID 28185141. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5394133/ ↩

  7. Owens DR, Bolli GB. The continuing quest for better subcutaneously administered prandial insulins. Diabetes Obes Metab (2020). PMID 31930670. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7187182/ ↩ ↩2 ↩3

  8. FDA / Novo Nordisk. NOVOLOG prescribing information — "the rate of insulin absorption and onset of activity is affected by the site of injection, exercise, and other variables." DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 ↩

  9. Nicolucci A, et al. Rapid-acting insulin analogues versus regular human insulin: a meta-analysis (post-meal glucose −22.2 mg/dL; HbA1c −0.13% in type 1 diabetes). Diabetes Ther (2019). PMID 31873857. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7048883/ ↩

  10. Riddell MC, et al. Exercise management in type 1 diabetes: a consensus statement (≈50% reduction of pre-exercise bolus for moderate activity). Lancet Diabetes Endocrinol (2017). PMID 28126459. https://pubmed.ncbi.nlm.nih.gov/28126459/ ↩

  11. FDA / Novo Nordisk. NOVOLOG prescribing information — subcutaneous injection, continuous subcutaneous infusion (pump), and intravenous use. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 ↩

  12. U.S. Food & Drug Administration. Biosimilar product information — insulin aspart-szjj (Merilog, Feb 2025) and the interchangeable insulin aspart-xjhz (Kirsty). FDA (2025). https://www.fda.gov/drugs/biosimilars/biosimilar-product-information ↩

Sources

  1. [1]NOVOLOG (insulin aspart) injection — full prescribing information · regulatory · 2000-06-07
  2. [2]NovoRapid (insulin aspart) — EMA European Public Assessment Report · regulatory · 1999-09-07
  3. [3]Fast-acting insulin aspart in Japanese patients with type 1 diabetes: faster onset… relative to insulin aspart (clamp comparison) · peer-reviewed · 2017-07-07
  4. [4]Pharmacokinetic properties of fast-acting insulin aspart administered in different subcutaneous injection regions · peer-reviewed · 2017-05-01
  5. [5]Rapid-acting insulin analogues versus regular human insulin: a meta-analysis of effects on glycemic control · peer-reviewed · 2019-12-23
  6. [6]The continuing quest for better subcutaneously administered prandial insulins · peer-reviewed · 2020-02-03
  7. [7]Exercise management in type 1 diabetes — a consensus statement · peer-reviewed · 2017-01-24
  8. [8]FDA biosimilar product information (insulin aspart-szjj, -xjhz) · regulatory · 2025-02-14