Insulin (Endogenous Peptide)
Also known as: Human Insulin, Proinsulin-derived, IRI
Overview
Insulin is a 51-amino acid peptide hormone produced by pancreatic beta cells, consisting of an A-chain (21 AA) and B-chain (30 AA) connected by two disulfide bonds. It is the master regulator of glucose metabolism and protein synthesis, functioning through the insulin receptor tyrosine kinase (INSR) to stimulate glucose uptake, glycogen synthesis, lipogenesis, and protein anabolism while suppressing lipolysis, glycogenolysis, and gluconeogenesis. Synthetic insulin analogs (fast-acting: lispro, aspart, glulisine; long-acting: glargine, detemir, degludec) have revolutionized diabetes management.
Mechanism of Action
Insulin binds the insulin receptor (INSR), a transmembrane tyrosine kinase that undergoes autophosphorylation and phosphorylates IRS-1/2 adapter proteins. This activates PI3K → PDK1 → Akt signaling, causing GLUT4 vesicle translocation to the plasma membrane (enabling glucose uptake in muscle and fat), glycogen synthase kinase-3 inhibition (promoting glycogen synthesis), and mTORC1 activation (stimulating protein synthesis). Simultaneously, Ras/MAPK/ERK activation mediates mitogenic effects. In the liver, insulin suppresses PEPCK and glucose-6-phosphatase (gluconeogenic enzymes), reducing hepatic glucose output.
Potential Benefits
- Essential treatment for type 1 diabetes
- Adjunct therapy in type 2 diabetes
- Powerful anabolic agent for muscle protein synthesis
- Glycogen synthesis promotion in muscle and liver
- Life-saving in diabetic ketoacidosis
Dosage Protocols
The following reflects doses used in published research studies. This is not medical advice. Consult a qualified healthcare professional.
| Beginner | Prescribed titration — not a self-managed peptide |
| Intermediate | N/A |
| Advanced | N/A |
| Cycle Duration | Chronic lifelong (T1D) |
Medical use ONLY. Insulin misuse is life-threatening. FDA-approved analogs: rapid (lispro, aspart, glulisine), short (regular), intermediate (NPH), long (glargine, detemir, degludec), ultra-long (degludec).
Use our Reconstitution Calculator to determine exact syringe units for your protocol.
Routes of Administration
Subcutaneous Injection Analog-dependent
Standard route via pen or syringe. Rotate sites.
Continuous Subcutaneous Insulin Infusion (pump) High, controlled
Pump-delivered rapid-acting analog.
Inhaled (Afrezza) ~25-30% — rapid onset
FDA-approved inhaled mealtime insulin.
Intravenous 100%
Hospital/ICU use only (e.g. DKA).
Read our full Routes of Administration Guide for detailed comparison of all delivery methods.
Stacking Protocols
Popular research stacks involving Insulin (Endogenous Peptide):
Basal-Bolus Regimen
Standard T1D and advanced T2D regimen — long-acting for basal coverage + rapid-acting with meals.
Amylin Co-therapy
Adjunct Pramlintide with mealtime insulin improves postprandial glucose.
Explore our complete Peptide Stacking Guide for more combinations and safety considerations.
Reconstitution
| Storage | Unopened: refrigerate 2-8°C. In-use: room temperature (up to 28-56 days depending on analog). |
|---|
Do not freeze. Discard if cloudy (except NPH) or clumped.
Need exact syringe measurements?
Amino Acid Sequence
A-chain: Gly-Ile-Val-Glu-Gln-Cys-Cys-Thr-Ser-Ile-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr-Cys-Asn; B-chain: Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Tyr-Leu-Val-Cys-Gly-Glu-Arg-Gly-Phe-Phe-Tyr-Thr-Pro-Lys-Thr
Side Effects & Safety
- Hypoglycemia (most dangerous; can be fatal)
- Weight gain
- Injection site lipodystrophy
- Hypokalemia at high doses
Safety & Contraindications
This information is for educational purposes only. Consult a qualified healthcare provider before using any peptide.
Bleeding Disorders
Active Skin Infection at Injection Site
FDA Safety Information
FDA labeling warns of hypoglycemia, hypokalemia, hypersensitivity reactions, and fluid retention when combined with thiazolidinediones.
Pharmacokinetics
| Half-Life | Endogenous: ~4-6 min. Analogs: lispro/aspart ~1 hr; glargine ~12-14 hr (flat); degludec ~25 hr |
|---|---|
| Storage | Unopened: refrigerate 2-8°C. Once in use: room temperature (<30°C) for 14-56 days depending on analog. Do not freeze. Protect from direct heat and sunlight. |
Synergistic Compounds
The following compounds have been studied alongside Insulin (Endogenous Peptide) for potential complementary or synergistic effects:
Learn More
References & Further Reading
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