How long does Human Growth Hormone stay in your system?
Human Growth Hormone has a published half-life of 7 to 10 hours apparent (subcutaneous); 21.1 minutes (intravenous). By the standard pharmacology rule of thumb, a drug is about 97% eliminated after roughly five half-lives, which here works out to between 35 and 50 hours. That uses the subcutaneous range. Intravenously the label gives 21.1 minutes, which by the same rule is about 105.5 minutes, or roughly 1.8 hours.
Source: Norditropin label, DailyMed · FDA label · measured: subcutaneous (apparent); intravenous infusion · dataset reviewed September 23, 2026
What is the half-life of Human Growth Hormone?
The Norditropin prescribing information gives somatropin, recombinant human growth hormone, two very different numbers: 7 to 10 hours apparent after subcutaneous injection, and 21.1 minutes after intravenous infusion. Both are correct, and the gap between them is the most instructive thing on this page.
The label states explicitly that the longer subcutaneous figure is due to slow absorption from the injection site. After a subcutaneous injection, hormone leaves the injection site more slowly than the body clears it, so the decline measured in blood reflects absorption rather than elimination. This is called flip-flop kinetics. The 21.1 minute intravenous value is the closest label-sourced proxy for how fast growth hormone itself is eliminated.
How much Human Growth Hormone is left after each half-life?
Each half-life removes half of whatever is left, so the percentages are pure arithmetic and the same for any compound; only the clock changes. For Human Growth Hormone, one half-life is 7 to 10 hours. The rows below run that forward for a single amount with nothing added.
| Half-lives elapsed | Time elapsed | Remaining | Cleared |
|---|---|---|---|
| 1 | 7 to 10 hours | 50% | 50% |
| 2 | 14 to 20 hours | 25% | 75% |
| 3 | 21 to 30 hours | 12.5% | 87.5% |
| 4 | 28 to 40 hours | 6.25% | 93.75% |
| 5 | 35 to 50 hours | 3.13% | 96.88% |
| 6 | 42 to 60 hours | 1.56% | 98.44% |
| 7 | 49 to 70 hours | 0.78% | 99.22% |
Why do the numbers differ between sources?
Growth hormone figures differ mainly because people quote different routes without saying so. A source that says minutes is describing intravenous administration. A source that says hours is describing a subcutaneous injection. They measure different things, and the route has to travel with the number.
Brand and formulation matter too. Our figure comes from the Norditropin label, and other somatropin products carry their own prescribing information. We have not averaged across brands, and we do not quote figures for products we have not checked.
What does a half-life not tell you?
Your pituitary releases growth hormone in pulses, so it is never absent. After an injection the half-life describes a return toward your own fluctuating baseline, which makes 'out of your system' a blurry idea for this compound in particular.
It also does not describe IGF-1. Much of growth hormone's effect is carried by IGF-1 made in the liver in response, and that downstream signal follows its own kinetics. Effects such as fluid retention, joint symptoms or changes in glucose handling reflect sustained exposure, not a single plasma curve.
Can you run the numbers yourself?
The estimator applies the same decay arithmetic to any half-life, starting amount and time you enter. It opens with Human Growth Hormone's published value loaded. Type another figure to see how sensitive the result is to it.
Published value: 7 to 10 hours apparent (subcutaneous); 21.1 minutes (intravenous) (Subcutaneous (apparent); intravenous infusion) · Norditropin label, DailyMed · Compound profile
Show the math
What are the limits of this estimate?
Everything above is a single-compartment approximation: one pool of drug, falling by the same fraction in every interval. Real elimination varies with kidney and liver function, body composition, formulation and route, and a published figure describes only the route and the people it was measured in. Many compounds also show a fast distribution phase before the slower elimination the table describes.
A half-life is not a dosing schedule. Labelled intervals come from clinical trials that measured outcomes and tolerability, and nothing on this page suggests when to take, repeat or stop anything. Whether Human Growth Hormone is out of your system for drug-testing purposes is a different question again. Tests often look for metabolites rather than the parent compound, and the answer depends on the assay, its sensitivity and the sample type, none of which a plasma half-life captures.
FAQ.
Why does growth hormone have two half-lives?
Because the route changes what is being measured. The Norditropin label gives 21.1 minutes intravenously, which reflects elimination, and 7 to 10 hours apparent subcutaneously, which the label attributes to slow absorption from the injection site.
Which number does the table on this page use?
The subcutaneous apparent range of 7 to 10 hours, the route the Norditropin product is given by. The intravenous figure of 21.1 minutes appears in the answer above for comparison. Neither describes IGF-1, which follows its own curve.
Can a half-life tell me whether growth hormone use would be detected?
No. Growth hormone is prohibited in sport by WADA, and detection depends on the specific test, what it measures and its sensitivity, not on the half-life of an injection. Growth hormone is also made naturally, which is part of why testing for it is complex. We do not publish detection windows.
For what the evidence on Human Growth Hormone actually shows, read the Human Growth Hormone profile. For approval and regulatory position, see is Human Growth Hormone legal. The half-life reference lists every sourced value side by side, including the compounds where a number circulates online with no reliable human data behind it.