How long does HCG stay in your system?
HCG has a published half-life of 29 ± 6 hours terminal (subcutaneous); 26.5 ± 2.5 hours (intravenous). By the standard pharmacology rule of thumb, a drug is about 97% eliminated after roughly five half-lives, which here works out to about 6 days. That uses the subcutaneous terminal mean. Intravenously the label gives 26.5 ± 2.5 hours, which by the same rule is about 132.5 hours, or roughly 5.5 days.
Source: Ovidrel label, DailyMed · FDA label · measured: subcutaneous or intravenous · dataset reviewed September 23, 2026
What is the half-life of HCG?
The Ovidrel prescribing information gives recombinant hCG, choriogonadotropin alfa, a terminal half-life of 29 ± 6 hours after subcutaneous injection and 26.5 ± 2.5 hours after intravenous injection. hCG is a glycoprotein hormone made by the placenta in pregnancy, and as a medicine it mimics luteinising hormone at the LH/hCG receptor.
The label describes the serum profile as two-compartment, with an initial half-life of 4.5 ± 0.5 hours as the hormone distributes, followed by the slower terminal phase. The table on this page uses the terminal value, so in the first hours after an injection it overstates how much remains, and it becomes a closer description afterwards.
How much HCG 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 HCG, one half-life is 29 hours. The rows below run that forward for a single amount with nothing added.
| Half-lives elapsed | Time elapsed | Remaining | Cleared |
|---|---|---|---|
| 1 | 29 hours | 50% | 50% |
| 2 | 58 hours | 25% | 75% |
| 3 | 3.6 days | 12.5% | 87.5% |
| 4 | 4.8 days | 6.25% | 93.75% |
| 5 | 6 days | 3.13% | 96.88% |
| 6 | 7.3 days | 1.56% | 98.44% |
| 7 | 8.5 days | 0.78% | 99.22% |
Why do the numbers differ between sources?
Most of the variation in hCG figures comes from different products. The values here are for recombinant choriogonadotropin alfa. Urinary hCG products such as Pregnyl carry no pharmacokinetics section on their labels at all, so there is no label figure for them to compare against.
Route matters a little as well, 29 hours subcutaneous against 26.5 hours intravenous, and the standard deviations are wide enough for individual values to overlap. Quoting one number without its product, route and spread hides most of the information.
What does a half-life not tell you?
hCG is the hormone that pregnancy tests detect, which gives 'out of your system' an unusually literal meaning here. A test that looks for hCG cannot tell whether it came from a pregnancy or an injection. The half-life describes how fast injected hCG declines, but not when a particular test stops detecting it, which depends on that test's sensitivity.
It also does not describe the testosterone or ovulation response. hCG acts on the gonads, and the hormonal changes it triggers follow their own course after the hCG itself has declined.
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 HCG's published value loaded. Type another figure to see how sensitive the result is to it.
Published value: 29 ± 6 hours terminal (subcutaneous); 26.5 ± 2.5 hours (intravenous) (Subcutaneous or intravenous) · Ovidrel label, DailyMed · Compound profile
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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 HCG 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.
Can an hCG injection affect a pregnancy test?
Pregnancy tests detect hCG, so injected hCG can be picked up while it remains in circulation. How long that lasts depends on the test's sensitivity as well as the half-life, so this page cannot give a reliable cut-off. The prescriber or the testing laboratory can.
Why is there no half-life for Pregnyl?
Urinary hCG products such as Pregnyl carry no pharmacokinetics section on their labels. The figures on this page are for recombinant choriogonadotropin alfa from the Ovidrel label, and we do not transfer them to products that were not measured.
What is the initial half-life of hCG?
The Ovidrel label describes a two-compartment serum profile with an initial half-life of 4.5 ± 0.5 hours, and gives a terminal half-life of 29 ± 6 hours after subcutaneous injection. The initial phase reflects distribution; the terminal phase is the slower elimination that dominates later.
For what the evidence on HCG actually shows, read the HCG profile. For approval and regulatory position, see is HCG 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.