Overview
Human Growth Hormone is a growth hormone-related peptide. Recombinant 191-amino acid polypeptide identical to endogenous growth hormone.
With a half-life of ~2.6 hours, Human Growth Hormone requires daily administration in most observed protocols. Administered via SubQ injection, it has a bioavailability of approximately 75% via its primary route.
Half-life approximately 2.6 hours. Subcutaneous bioavailability approximately 75%. Pharmaceutical brands: Genotropin, Norditropin, Humatrope. One-compartment model.
Mechanism of Action
Human Growth Hormone's pharmacological activity involves the following key pathways:
Direct GH Replacement
Human Growth Hormone is a recombinant form identical to endogenous growth hormone. It directly activates GH receptors throughout the body, bypassing the hypothalamic-pituitary axis entirely.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
1 IU/day
Route
Subcutaneous
Frequency
2-3 times daily
Duration
4-12 weeks
Dose
6 IU/day
Route
Subcutaneous
Frequency
2-3 times daily
Duration
4-12 weeks
Reconstitution Steps
Human Growth Hormone is supplied as a lyophilized (freeze-dried) powder and requires reconstitution before use. Common vial sizes: 4 IU (1.33 mg), 10 IU (3.33 mg), 12 IU (4 mg), 16 IU (5.33 mg), 36 IU (12 mg).
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1
Gather supplies
You will need a vial of lyophilized HGH powder, bacteriostatic water (BAC water), an insulin syringe (0.5 mL or 1 mL), two alcohol swabs, and a sharps container. HGH is sensitive to agitation and temperature — handle with care throughout.
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2
Clean the vial tops
Wipe the rubber stoppers on both the HGH vial and the BAC water vial with separate alcohol swabs. Allow both to dry for 10–15 seconds before piercing with a needle.
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3
Draw bacteriostatic water
For a standard 10 IU vial, draw 1 mL of BAC water — this produces a clean 10 IU/mL concentration where every 0.1 mL (10 units on an insulin syringe) equals exactly 1 IU. For larger 20 IU vials, 2 mL BAC water maintains the same convenient 10 IU/mL ratio.
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4
Inject water slowly against the glass wall
Insert the needle at a low angle and direct the BAC water to flow down the inner glass wall of the HGH vial — not directly onto the lyophilized cake. HGH is particularly sensitive to mechanical agitation; this technique prevents foaming and denaturation.
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5
Gently swirl — never shake
After all water is added, swirl the vial very gently in a circular motion for 15–30 seconds. Do not shake, vortex, or roll vigorously. The powder should dissolve to produce a clear, colorless solution — this may take 1–2 minutes.
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6
Label, refrigerate, and avoid light
Label the vial with the reconstitution date and store immediately in the refrigerator at 2–8°C. Reconstituted HGH should be used within 3–4 weeks and must never be frozen. Keep away from direct light and avoid temperature fluctuations.
Quick Reconstitution Math
10 IU vial + 1 mL BAC water = 10 IU/mL. A 2 IU dose = 0.2 mL (20 units on an insulin syringe). A 4 IU dose = 0.4 mL (40 units). Use the Milligram reconstitution calculator for custom vial sizes.
Refrigerate reconstituted solution at 2–8°C. Use within 3–4 weeks. Never freeze the reconstituted solution — freeze-thaw cycles denature the protein. Lyophilized powder prior to reconstitution can be stored at −20°C. Protect from light and avoid agitation.
Frequently Asked Questions
What is recombinant HGH (Somatropin) and how does it differ from GH peptides?
Recombinant human growth hormone (rHGH), sold under brand names including Genotropin, Humatrope, Norditropin, and Saizen, is a 191–amino acid protein identical in structure to endogenous human GH produced via recombinant DNA technology. Unlike GH secretagogue peptides such as CJC-1295, Ipamorelin, or Sermorelin–which stimulate the pituitary to release its own GH–somatropin directly replaces or supplements GH levels exogenously. This means it bypasses the pituitary entirely and is not subject to natural somatostatin feedback regulation.
What is the half-life of HGH and does timing of injection matter?
Somatropin administered subcutaneously has a terminal half-life of approximately 3–4 hours, though its metabolic half-life at the tissue level is only 20–30 minutes. The prolonged plasma half-life after SubQ injection reflects slow absorption from the injection depot rather than prolonged circulation. Morning injection is commonly observed for body composition goals to align with the natural cortisol and insulin cycle, while some protocols use pre-sleep injection to mimic the body's natural nocturnal GH pulse. Both IM and SubQ routes are used, with SubQ being more common for daily protocols.
How much HGH is typically used and what does IU mean?
HGH potency is measured in International Units (IU), where approximately 1 mg equals 3 IU by pharmacopeial standard. For body composition purposes, 2–4 IU/day is the most commonly observed dose range, with 4–6 IU/day reported among more advanced users. Medical replacement doses for adult GH deficiency typically start at 0.2–0.4 mg/day (0.6–1.2 IU/day). The dose–response relationship is non-linear–incremental gains in IGF-1 and body composition diminish at higher doses while side effect incidence increases.
How long does HGH take to produce noticeable changes?
Subtle changes in sleep quality, skin texture, and recovery are commonly reported within the first 2–4 weeks of use. Objective shifts in body composition–measurable lean mass gain and fat reduction–typically require 3–6 months of consistent daily administration. Longer run durations of 6–12 months are frequently observed in the community for meaningful and sustained body composition outcomes. IGF-1 levels typically show measurable increases within 2–4 weeks and serve as a useful biological confirmation of dosing efficacy.
How is lyophilized HGH powder reconstituted?
Lyophilized somatropin vials are most commonly reconstituted with bacteriostatic water (BAC water), though some pharmaceutical formulations include a specific diluent. For a standard 10 IU vial, adding 1 mL of BAC water produces a concentration of 10 IU/mL–simplifying dose math so that 0.1 mL (10 units on an insulin syringe) equals exactly 1 IU. The water should be injected slowly against the glass wall of the vial, followed by gentle swirling rather than shaking, as HGH is sensitive to agitation.
What compounds is HGH commonly stacked with?
HGH is frequently combined with GH secretagogue peptides such as CJC-1295, Ipamorelin, or Sermorelin, which continue stimulating endogenous GH pulsatility alongside the exogenous supply. BPC-157 and TB-500 are commonly added for connective tissue and recovery support, particularly given that higher HGH doses can place stress on tendons and joints as lean mass accrues rapidly. In more advanced protocols, HGH is sometimes run alongside testosterone or other compounds for additive body composition effects.