Insulin aspart

Rapid-acting insulin analogue

ATC code: A10AB05

Brand names: NovoLog, Fiasp

Updated 24 Sep 2026 · Methodology

Indications

Insulin-dependent type 2 diabetes mellitus

Second line

In type 2 diabetes prandial insulin is added to basal when fasting glucose is already at target but is not and the rises land after meals. It usually starts with a single aspart injection at the meal with the largest glucose excursion and expands as needed. The sulfonylurea is revisited at the same time: keeping a secretagogue alongside prandial insulin stacks two mechanisms that lower glucose regardless of food. The AEMPS NovoRapid label names oral antidiabetic drugs among agents that potentiate the hypoglycaemic effect. Metformin usually stays.

Sources

ICD-10: E11.9 · ICD-11: 5A11

Type 1 diabetes mellitus

First line

Aspart covers the post-meal glucose rise in a basal-bolus regimen and runs in insulin pumps. The AEMPS NovoRapid label places the injection immediately before the meal, or right after it when needed, and approves the product from 1 year of age. The dose is calculated against the carbohydrate of that particular meal rather than fixed for every day. A short action demands discipline: if the meal does not happen after the injection, hypoglycaemia arrives within an hour or two. The niacinamide formulation starts earlier and is given closer to the first bite. In a pump, aspart provides both basal and bolus delivery, and a catheter occlusion there turns into ketosis within hours.

Sources

ICD-10: E10 · ICD-11: 5A10

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Muscle mass gain (bodybuilding self-use)

Not recommended

In gym regimens rapid insulin is injected after training together with carbohydrates, on the idea of driving glucose and amino acids into muscle. No regulator has approved that use, there are no studies of muscle gain in people without diabetes, and in someone with intact insulin secretion the gap between a working and a dangerous dose is minimal. Aspart starts within 10–20 minutes and peaks in the first hours: hypoglycaemia comes fast and unfolds during the workout or in sleep. Cases with seizures, coma and irreversible brain damage in healthy men are documented. Eating carbohydrates does not insure against it – absorption cannot keep pace with the injection. If insulin has been recommended for muscle growth, consider seeking a second opinion from an endocrinologist.

Sources

AEMPS: Ficha técnica NovoRapid FlexPen 100 U/ml solución inyectable (2023)

How to read tiers A–F

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit

Mechanism of action

In aspart, proline B28 is replaced by aspartic acid. The negative charge keeps hexamers from holding together, so in subcutaneous tissue the product breaks into monomers that absorb at once. Action starts within 10–20 minutes, peaks at 1–3 hours and lasts 3–5 hours – a profile that mirrors pancreatic secretion at a meal far more closely than human regular insulin. The niacinamide formulation (faster aspart) absorbs earlier still. A fast onset also means fast hypoglycaemia if the dose is wrong or a meal is skipped.

Safety

Contraindications

Hypoglycaemia
Hypersensitivity to insulin or to any excipient of the product

Serious adverse effects

Severe hypoglycaemia with loss of consciousness and seizures
Hypokalaemia in overdose, up to rhythm disturbance
Anaphylaxis and generalised insulin allergy
Oedema and decompensated heart failure when combined with pioglitazone

Common adverse effects

Hypoglycaemia: sweating, tremor, palpitations, hunger, confusion
Injection site reactions: redness, swelling, itching
Lipohypertrophy when injections stay in one spot
Weight gain early in treatment

Pregnancy: can you take Insulin aspart?

Insulin does not cross the placenta and remains the mainstay of glycaemic control in pregnancy. Requirements shift by trimester: usually lower in the first, rising from the second, and falling sharply after delivery. The dose is revisited at every stage.

Breastfeeding: can you take Insulin aspart?

The label sets no restriction during breastfeeding: insulin is broken down in the infant's gut and does not reach the bloodstream. Insulin requirements often fall during lactation, so the dose is retitrated.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Label mentions9 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

ModeratePioglitazone
«Combinación de pioglitazona e insulinas: Se han notificado casos de insuficiencia cardiaca congestiva al usar pioglitazona en combinación con insulina, especialmente en pacientes con factores de…»
AEMPS, section 4.4 · Open on CIMA
anticonceptivos hormonalesclass named in the label
«Anticonceptivos orales, tiazidas, glucocorticoides, hormonas tiroideas, simpaticomiméticos, hormona de crecimiento y danazol.»
AEMPS, section 4.5 · Open on CIMA
antidiabéticos oralesclass named in the label
«Antidiabéticos orales, inhibidores de la monoamino oxidasa (IMAOs), betabloqueantes, inhibidores de la enzima conversora de la angiotensina (IECAs), salicilatos, esteroides anabólicos, sulfonamidas y…»
AEMPS, section 4.5 · Open on CIMA
betabloqueantesclass named in the label
«Antidiabéticos orales, inhibidores de la monoamino oxidasa (IMAOs), betabloqueantes, inhibidores de la enzima conversora de la angiotensina (IECAs), salicilatos, esteroides anabólicos, sulfonamidas y…»
AEMPS, section 4.5 · Open on CIMA
corticosteroidesclass named in the label
«Anticonceptivos orales, tiazidas, glucocorticoides, hormonas tiroideas, simpaticomiméticos, hormona de crecimiento y danazol.»
AEMPS, section 4.5 · Open on CIMA
IMAOclass named in the label
«Antidiabéticos orales, inhibidores de la monoamino oxidasa (IMAOs), betabloqueantes, inhibidores de la enzima conversora de la angiotensina (IECAs), salicilatos, esteroides anabólicos, sulfonamidas y…»
AEMPS, section 4.5 · Open on CIMA
inhibidores de la ECAclass named in the label
«Antidiabéticos orales, inhibidores de la monoamino oxidasa (IMAOs), betabloqueantes, inhibidores de la enzima conversora de la angiotensina (IECAs), salicilatos, esteroides anabólicos, sulfonamidas y…»
AEMPS, section 4.5 · Open on CIMA
simpaticomiméticosclass named in the label
«Anticonceptivos orales, tiazidas, glucocorticoides, hormonas tiroideas, simpaticomiméticos, hormona de crecimiento y danazol.»
AEMPS, section 4.5 · Open on CIMA
tiazidasclass named in the label
«Anticonceptivos orales, tiazidas, glucocorticoides, hormonas tiroideas, simpaticomiméticos, hormona de crecimiento y danazol.»
AEMPS, section 4.5 · Open on CIMA

Check interaction with another drug

Opens the checker prefilled with this drug. Pick the second one from your regimen.

Open checker

Summary of a multi-drug list →

Medicine list: everything you take in one place →

Frequently asked

What is Insulin aspart used for?

Insulin aspart is evaluated for the following indications with varying evidence strength: Type 1 diabetes mellitus (evidence tier A), Insulin-dependent type 2 diabetes mellitus (evidence tier A), Muscle mass gain (bodybuilding self-use) (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Insulin aspart?

Common side effects of Insulin aspart (≥ 1 in 100): Hypoglycaemia: sweating, tremor, palpitations, hunger, confusion, Injection site reactions: redness, swelling, itching, Lipohypertrophy when injections stay in one spot, Weight gain early in treatment. See the Safety section for uncommon and serious reactions.

Is Insulin aspart safe during pregnancy?

Is Insulin aspart compatible with breastfeeding?

Who should not take Insulin aspart?

Insulin aspart is contraindicated in: Hypoglycaemia; Hypersensitivity to insulin or to any excipient of the product. Full list in the Safety section.

Official sources

Direct links to regulator labels. Open in a new tab.

AEMPS / CIMA

Other drugs in this group

Insulin degludec, Insulin detemir, Insulin glargine, Insulin glulisine, Metformin, Sitagliptin + Metformin, Empagliflozin, Insulin human isophane (NPH)