HGH Dosage Calculator (IU to mg)

You are holding a vial that says 10 IU and a pen cartridge that says 5 mg. They are the same drug. For somatropin, 1 mg equals 3 IU, so the 5 mg cartridge holds 15 IU and the 10 IU vial holds 3.33 mg.

Milligrams measure mass. International Units measure biological activity against a reference preparation. Think of a car engine rated in horsepower and in litres of displacement: two scales for one engine, linked by a fixed ratio for that model. For growth hormone the ratio is set by the WHO International Standard for somatropin, which assigns 3 IU to every milligram of pure protein (PMID 11580214).

The ratio only holds for somatropin. Insulin runs at roughly 27.5 IU per mg and HCG at about 10,000 IU per mg, so an IU of one hormone says nothing about an IU of another. The peptide unit converter carries each factor if you need the others.

Pharmacy products are labeled in milligrams because that is how the prescription is written: 4 mg, 5 mg and 12 mg pens translate to 12, 15 and 36 IU. Generic lyophilized somatropin is labeled in IU and usually ships as a kit of ten 10 IU vials, 100 IU in the box, with 4 IU vials sold for low-dose use.

The label changes the arithmetic and nothing else. A 12 mg cartridge contains the same hormone as 3.6 of the 10 IU vials. What differs is the diluent: pens arrive pre-mixed at a fixed concentration, while a powder vial is whatever concentration you make it.

Concentration is IU in the vial divided by millilitres of water. A 10 IU vial with 1 mL of bacteriostatic water is 10 IU/mL, and a U-100 insulin syringe holds 100 units per mL, so each IU is 10 units on the barrel. A 2 IU dose is 20 units. Add 2 mL instead and the same 2 IU becomes 40 units.

The mistake that matters: you mixed last month's vial with 2 mL and drew 40 units for 2 IU. This month you add 1 mL, keep drawing 40 units, and inject 4 IU, double the intended dose, for as long as the vial lasts. At 4 IU per day that is the range where trials recorded swollen ankles and numb fingers within weeks (PMID 17227934). Fix: write the water volume on the vial with a marker the moment you mix it.

For any other vial and water combination, the peptide reconstitution calculator runs the same division. Once mixed, the vial lives in the fridge; the HGH storage guide covers how long it stays potent.

The body releases its largest growth hormone pulse in the first hours of sleep (PMID 10984255). That single fact drives both camps. Some users inject before bed to add to that pulse. Others inject on waking, fasted, so the night-time pulse runs on its own.

Above 3 to 4 IU per day, users commonly split the dose, half on waking and half before bed, to reduce water retention. Growth hormone raises blood glucose and free fatty acids for several hours after a dose (PMID 19240267), which is why fasted morning injections are the more frequent report. No controlled trial has compared these schedules for body composition, so every schedule above is reported practice without trial support.

Clinicians do not dose growth hormone by body weight in adults. The Endocrine Society and AACE guidelines start low, 0.1 to 0.4 mg per day depending on age, then adjust every 1 to 2 months until serum IGF-1 sits inside the normal range for age, and lower the dose when it drifts above (PMID 21602453, PMID 31760824).

Fasting glucose and HbA1c are the second check. Growth hormone opposes insulin at the liver and muscle, so insulin sensitivity falls at any effective dose (PMID 19240267). Anyone with diabetes or prediabetes needs that interaction managed by their prescriber before the first injection.

The effects of too much growth hormone are dose-dependent and well described: soft tissue edema, carpal tunnel syndrome, arthralgia, gynecomastia and impaired fasting glucose or new-onset diabetes. In a systematic review of 31 trials in healthy older adults, the groups receiving growth hormone at a mean of 14 mcg/kg per day, about 1 mg or 3 IU daily, had markedly higher rates of every one of those effects than placebo (PMID 17227934).

That is the basis of the caution banner in the calculator: once a schedule exceeds 21 IU per week, it exceeds 1 mg per day, which is above adult replacement and inside the range where those trials saw harm. A separate review of 27 studies in young athletes found more lean mass but no gain in strength or exercise capacity, and more fatigue and edema (PMID 18347346).

Somatropin is a prescription-only medicine. In the United States, federal law restricts its distribution to approved indications, so supply for anti-aging or bodybuilding use is unlawful, and it sits on the WADA prohibited list in sport (PMID 31180479). Active cancer, diabetic retinopathy and acute critical illness are contraindications in every guideline. Nothing on this page replaces a prescriber who can order IGF-1 and glucose panels and adjust the dose against them.