Calculation of remaining HCG concentration after injection
Human Chorionic Gonadotropin (HCG) is a hormone that plays a central role in both fertility treatment and pregnancy detection. If you have received an HCG injection such as Ovitrelle®, Pregnyl®, or Novarel®, you may be wondering: When will the injected HCG be cleared from my body? Our HCG calculator helps you get an estimate.
HCG is used in fertility treatment to trigger ovulation. It mimics luteinizing hormone (LH) and signals the ovaries to release the mature egg. This is crucial for timing intercourse or insemination. At the same time, HCG is also the hormone detected in pregnancy tests – both in blood and urine.
Half-life describes the time the body needs to break down half of a substance. For HCG, this typically ranges between 24 and 40 hours, depending on individual metabolism. A fast metabolism leads to a half-life of about 26-28 hours, while a slow metabolism can mean up to 36-40 hours.
This is the most common question! After an HCG injection, a pregnancy test can still show positive for days even without a pregnancy. To avoid a false-positive result, you should wait until the injected HCG is completely cleared. For a typical Ovitrelle® dose of 6,500 IU, this can take 10-14 days. Our calculator shows you exactly when you can test.
HCG is first detectable in blood and appears in urine about one day later. The urine concentration is about 60% of the previous day's blood value. This is why blood tests can detect pregnancy earlier than urine tests. Our calculator considers both values.
Pregnancy tests have different sensitivities. High-sensitivity tests can detect HCG from 10 IU/L, while standard tests only react from 25 IU/L. For testing out the HCG injection, this means: With a 10 IU/L test, you need to wait longer for a reliable result. Our color code shows you when each test type should be safely negative.
Sometimes an additional "booster" injection is given after the initial HCG shot to support the corpus luteum and maintain progesterone production. This additional dose extends the time until all HCG is cleared. Our calculator also considers booster injections and calculates the combined breakdown of both doses.
The amount of HCG varies depending on the medication and prescription. Here are the most common HCG injections and their typical dosages: • Ovitrelle® (Choriogonadotropin alfa): 6,500 IU (250 µg) – recombinant hCG, most commonly used for ovulation triggering • Pregnyl®: 5,000 or 10,000 IU – urinary hCG • Novarel®: 5,000 or 10,000 IU – urinary hCG • Brevactid®: 1,500, 3,000, or 5,000 IU – urinary hCG, various dosages available • Choriomon®: 5,000 or 10,000 IU – urinary hCG • Choragon®: 1,500, 5,000, or 10,000 IU – urinary hCG • Profasi®: 5,000 or 10,000 IU – urinary hCG (discontinued in some regions) For a "Double Trigger" or "Dual Trigger" protocol, two Ovitrelle® injections are often combined (13,000 IU) for enhanced ovulation stimulation. Always enter your actual dose in the calculator, as this directly affects the breakdown time.
The peak serum level of hCG after an injection is estimated using pharmacokinetic data from scientific studies, not simply by dividing the dose by body volume. Research shows that after a subcutaneous injection, only part of the administered dose appears in the bloodstream at once because the hormone is absorbed gradually and distributed into body fluids. Clinical studies consistently demonstrate that a 6,500 IU recombinant hCG dose produces a peak of about 150–200 IU/L, while 10,000 IU urinary hCG produces around 330–340 IU/L. Based on these observed real-world dose–concentration relationships, a practical approximation is: Peak hCG (IU/L) ≈ 0.03 × Injected IU. For example, a double trigger of 13,000 IU results in an estimated peak of ~390 IU/L, which matches published pharmacokinetic profiles.
With a standard dose of 6,500 IU Ovitrelle® and an average half-life of 32 hours, the injected HCG is below the detection limit of most tests after about 10-12 days. With fast metabolism, it can be as early as 8-9 days.
Pregnyl® contains different amounts of HCG depending on the dosage (5,000 or 10,000 IU). Use our calculator with your exact dose to calculate the breakdown date. As a rule of thumb: the lower the dose, the faster the breakdown.
Yes, but with caution! Many women test daily to see if the test gets weaker ("testing out the trigger"). If the test gets weaker day by day, it's the injected HCG. If it gets stronger or stays the same, pregnancy might be present.
A positive test after HCG injection can mean: 1) The injected HCG hasn't fully cleared yet, or 2) You are pregnant and your body is producing its own HCG. Compare with our calculator to see if the value is still in the expected breakdown range.
Yes, body weight can influence the distribution and breakdown of HCG. People with higher weight often have a larger volume of distribution, which can slightly slow down the breakdown. However, individual metabolism rate plays a bigger role.
The blood test (Beta-HCG) is more accurate and can detect lower concentrations. Urine tests react delayed and at higher thresholds. For monitoring HCG breakdown, however, urine tests are more practical for daily use.