About HGH (Somatropin)

Human Growth Hormone (HGH) — also called somatropin — is a 191-amino acid polypeptide produced by the anterior pituitary. Pharmaceutical-grade recombinant HGH (rHGH) is structurally identical to the endogenous form. Unlike GHRH analogues such as Tesamorelin or CJC-1295, exogenous HGH bypasses the pituitary entirely and supplies GH directly into circulation.

HGH is studied extensively for GH-deficiency replacement, tissue recovery, body composition modulation, and downstream IGF-1 elevation. It’s a high-impact compound — both effect size and physiological cost are larger than secretagogue alternatives. Research protocols emphasise conservative starting doses and monitoring of insulin sensitivity, blood glucose, and IGF-1 levels.

Dosing observed in research literature

Application	Dose	Frequency	Notes
Sensitivity / starting protocol	1 IU / day	Once daily, AM	Used for first 2–4 weeks to assess tolerance
Standard research dose	2 IU / day	Once daily AM, or split AM/PM	Most common in body-composition research
Higher-range research	4 IU / day	Split 2 IU AM + 2 IU PM	Increased insulin-resistance monitoring required

IU vs mg: 1 mg of recombinant somatropin ≈ 3 IU (more precisely 1 mg = 2.7–3.0 IU depending on manufacturer’s assay). A “10 IU vial” therefore contains approximately 3.3 mg of HGH.

Research cycles run 3–6 months minimum — HGH’s downstream effects (IGF-1 elevation, body composition changes) require sustained exposure to register in measurable endpoints. Some protocols extend to 12 months. Off-periods of 8–12 weeks are studied to assess endogenous GH axis recovery.

Typical reconstitution protocols

HGH vials are commonly sold in 10 IU and 36 IU sizes (some pens contain 15 IU per cartridge). Reconstitution targets a draw size that’s easy to read on a U-100 syringe and lets the vial last through its 21-day shelf-life window.

Vial size	Recommended BAC water	Concentration	1 IU draw	2 IU draw
10 IU	1 mL	10 IU / mL	10 units (U-100)	20 units
10 IU	2 mL	5 IU / mL	20 units	40 units
36 IU	1 mL	36 IU / mL	~3 units (low precision)	~6 units
36 IU	2 mL	18 IU / mL	~6 units	~11 units
36 IU	3.6 mL	10 IU / mL	10 units	20 units

For a 10 IU vial, 1 mL of BAC water keeps the maths clean — every “1 IU” is 10 units on the syringe. For a 36 IU vial, 3.6 mL gives the same clean 10 units per IU but uses more BAC water; alternatively, 2 mL gives 18 IU/mL with slightly larger draws.

Half-life and frequency

Plasma half-life of exogenous somatropin is 2–4 hours after subcutaneous injection. The downstream IGF-1 response, however, persists for 18–24 hours, which is why once-daily dosing is effective despite the short plasma window. Morning dosing is the most common in research literature because it allows IGF-1 elevation throughout the day; split dosing (AM + PM) at higher total doses spreads the metabolic load.

Storage and shelf life

Lyophilised: store at 2–8°C refrigerated. Some manufacturers permit room-temperature storage of the dry powder for short periods — check the supplier’s COA. Reconstituted: refrigerated, stable for ~21 days. HGH is more thermolabile than smaller peptides, so refrigeration discipline matters more here. Never freeze either the dry or reconstituted vial.

Frequently asked questions

How do I convert IU to mg for HGH?

The standard conversion is 1 mg ≈ 3 IU for somatropin. So a 10 IU vial contains ~3.3 mg of HGH, and a 36 IU vial contains ~12 mg. The calculator at the top of this page handles both units; switch the input mode based on how your vial is labelled.

Should I take HGH in the morning or evening?

Most research protocols use morning dosing because endogenous GH pulses are highest at night — taking exogenous HGH in the AM avoids dampening the natural nighttime release. For split-dose protocols (e.g. 2 IU AM + 2 IU PM), the second dose is usually administered late afternoon, not late evening, for the same reason.

What’s the difference between HGH and Tesamorelin?

HGH is the hormone itself, supplied exogenously. Tesamorelin is a GHRH analogue — it stimulates the pituitary to release endogenous GH. HGH produces a larger absolute IGF-1 increase but suppresses the natural GH axis. Tesamorelin produces a more physiological response but a smaller absolute peak.

Does HGH affect insulin sensitivity?

Yes, consistently — HGH increases hepatic glucose output and reduces peripheral insulin sensitivity. Research protocols at doses above 2 IU/day commonly monitor fasting glucose, HbA1c, and fasting insulin. The effect is dose-dependent and largely reversible after washout.

Can HGH be combined with IGF-1 LR3?

Some research protocols combine the two — HGH for endogenous IGF-1 elevation across the body, plus exogenous IGF-1 LR3 for additional receptor-binding pool. Combined dosing typically keeps both at the lower end of their ranges (HGH 1–2 IU, IGF-1 LR3 20 mcg) due to additive hypoglycaemic potential.

How long does HGH take to show effects?

IGF-1 elevation in research is measurable within 2 weeks. Body-composition changes typically require 8+ weeks of continuous dosing to register. Connective-tissue and recovery effects are reported earlier (2–4 weeks) in some research literature but are harder to quantify objectively.

What injection site is used for HGH research?

Subcutaneous abdominal injection is standard. Site rotation across the abdominal quadrants is recommended over multi-month cycles to prevent lipoatrophy at frequently-used spots.

Related compounds

HGH is the upstream anchor of the growth and performance category. Related: Tesamorelin (GHRH approach — stimulate endogenous GH), Ipamorelin + CJC-1295 (GHRP + GHRH secretagogue stack), IGF-1 LR3 (downstream IGF-1 supplementation). Full category: HGH.