HCG half-life and steady state
33 h modelled half-life, peaking 6 h after a dose. What that means for how long it lasts, how much it builds up, and when bloodwork is worth drawing.
- Also known as
- Human Chorionic Gonadotropin
- Class
- Ancillaries — AIs and SERMs
- Modelled half-life
- 33 h
- Time to peak
- 6 h
- Formulation
- Aqueous (reconstituted powder)
- Cleared per dosing interval
- 69% gone, 31% still present after 2.3 days
- Time to steady state
- ~6.9 days (about five half-lives)
- Accumulation at that cadence
- 1.45× a single dose
- Peak-to-trough at steady state
- 2.79×
- Regulatory status
- FDA approved for female infertility and cryptorchidism. Off-label for male TRT support.
- Monitoring panel
- E2 (HCG aromatizes significantly), Total T. LH/FSH will be suppressed — this is expected.
- Before mixing
- Sealed powder tolerates room temperature in transit, but keep it refrigerated at 2–8 °C (36–46 °F) for anything beyond a few weeks, or frozen for months. Keep it dark — the carton it shipped in is doing a job.
- After mixing
- Once reconstituted with bacteriostatic water: refrigerate at 2–8 °C and use within about 28 days. The benzyl alcohol in bacteriostatic water is what buys that window — plain sterile water has no preservative, so a vial mixed with it should be treated as one sitting only. Kits are usually ten vials: only the one you mixed is on that 28-day clock — the sealed ones keep their own, much longer shelf life, so store them as powder, not as solution.
- What ruins it
- Do not freeze a reconstituted vial. Repeated freeze–thaw is one of the more reliable ways to degrade a peptide.
- Handling caveat
- General handling practice for this formulation. Your supplier’s own insert or COA overrides anything here.
HCG's roughly thirty-three-hour half-life is long for a glycoprotein hormone, and the reason is its sugars. Human chorionic gonadotropin is heavily glycosylated, and those carbohydrate chains — particularly the sialic acid on them — slow its clearance from the kidney dramatically. Luteinising hormone, which HCG mimics at the same receptor, is cleared in about twenty minutes. Same receptor, a half-life two orders of magnitude apart, entirely because of the glycosylation.
That difference is the whole clinical point, and it is also the main caution. Endogenous LH arrives in pulses every couple of hours; HCG at a three-times-weekly cadence accumulates and produces continuous stimulation of the testicular Leydig cells instead. Continuous is what makes it useful for maintaining testicular volume and function during testosterone therapy — and continuous stimulation of a receptor is also the mechanism by which receptors downregulate, which is why the doses in the app's entry are in the hundreds of international units rather than the thousands.
Two things to watch follow directly from the curve. HCG-driven testicular testosterone production aromatises, so oestradiol can rise on a dose that leaves total testosterone barely changed — the app's monitoring note for it names E2 first for exactly this reason. And LH and FSH will read suppressed on any panel drawn while HCG is in use, which is expected rather than a finding: the pituitary is responding to the testosterone downstream, and the assay may cross-react with HCG itself.
One dose
pkCurve function — a
one-compartment absorption-and-elimination model with the absorption rate fitted so the
peak lands at the published time to peak.Dosed three times weekly
Charted at three times weekly because that is the schedule in the app's own dosing rows for fertility support on TRT. It is what the numbers below are indexed to, not a recommendation about frequency — that is a prescribing decision.
The arithmetic behind those numbers
fraction left after one interval = 2^(−1.70) = 0.308
accumulation ratio = 1 ÷ (1 − 0.308) = 1.45
time to steady state ≈ 5 × half-life = 6.9 days
peak-to-trough = simulated, 1.466 ÷ 0.5252 = 2.79
The accumulation ratio is a closed form; the peak-to-trough figure is not. The generator adds up enough repeated curves for the total to stop changing, then reads the highest and lowest points of the last interval — which is what steady state means in practice. The vertical axis is relative, not a concentration: the shape and the ratios carry across people, the absolute levels do not.
Interaction rules that name HCG
From the app's own interaction data. Not exhaustive, and not a safety clearance — a combination that is not listed is one nobody has documented here, which is not the same as one that is fine. The full combination checker has the rest.
HCG Must Stop Before PCT SERMs Begin
HCG should be used during the last 2 weeks of a cycle to prime the testes, then stopped completely before starting Nolvadex or Clomid. Running HCG concurrently with SERMs blunts the PCT response by continuing LH suppression via HCG's action.
What to watch: Timing critical: Stop HCG, wait 2 weeks after last long-ester injection, then start SERMs.
HCG Must Stop Before PCT SERMs Begin
Same as above — HCG and SERMs work at cross purposes during PCT. HCG ends the cycle phase; SERMs begin the PCT phase. They should not overlap.
What to watch: Sequential use only: HCG during cycle, SERMs after.
Gonadorelin and HCG — Choose One for Testicular Maintenance
Both gonadorelin and HCG serve the same purpose on TRT — preserving testicular function. Gonadorelin stimulates LH/FSH from the pituitary; HCG mimics LH directly at the testes. Using both simultaneously is redundant and may cause over-stimulation. Choose one approach.
What to watch: Total T, LH, FSH, E2, testicular volume. Monitor prolactin — over-stimulation can elevate it.
The dosing rows this cadence came from
Established clinical use Reproduced from the app's entry so you can see what the chart above is indexed to. Which row applies to a particular person, if any, is a clinical decision this page does not make.
| Label | Amount | Route and frequency |
|---|---|---|
| Fertility on TRT | 250-500IU | 2-3x per week SubQ |
When to draw bloodwork
The panel the app records for HCG is: E2 (HCG aromatizes significantly), Total T. LH/FSH will be suppressed — this is expected.. The pharmacokinetic point is the timing rather than the list: after any change, a level takes about 6.9 days to settle, so a panel drawn sooner measures something still moving. And because the peak-to-trough swing here is 2.79×, when in the interval you draw changes the result materially — a result without a stated draw time relative to the last dose is hard to compare with anything. Whether a result means anything is a question for the clinician who ordered it, read against the reference range your own lab printed. The lab-marker pages cover what the individual analytes measure.
Related: the interactive half-life calculator to try other cadences.
The app draws this curve from the doses you actually logged — your dates, your cadence — and projects seven days forward from the last one.
Save this dose to your log