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Ask a Fertility Nurse: Does HCG Interfere with HPT?

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by Gina Paoletti-Falcone, RN, BSN, Freedom Fertility Pharmacy, August 12, 2010


I have heard that the HCG injection can interfere with HPT (home pregnancy test) results. How long after I take my HCG injection can I do an HPT and get accurate results?

Nurse Gina Says:

HCG products include Generic HCG, Novarel, Ovidrel and Pregnyl. These medications are used to induce the final maturation of the egg so it can separate from the cells within the follicle and be released or ovulated 36 to 40 hours after the injection. In IUI cycles we use HCG products to reliably make ovulation occur on a given day and schedule the insemination on that day. In IVF cycles the HCG injection is given about 34 hours before the scheduled egg retrieval since we do not want ovulation to occur before the retrieval. HCG is necessary in IVF cycles so that the eggs separate from the cells within the follicles and can be retrieved. If you attempt to retrieve eggs without using HCG, you would simply get follicular fluid and no eggs.

But what is HCG? It is Human Chorionic Gonadotropin, the same hormone that a pregnancy secretes and exactly what we test for when we do a pregnancy test either using blood or urine. HCG can be used to mature eggs and induce ovulation because it is very similar in structure and function to the LH (luteinizing hormone) molecule that causes ovulation in a natural menstrual cycle. LH is the hormone that you are looking for a “surge” of if you have ever used an OPK (ovulation predictor kit). In general, hormones that we have in our blood are excreted in our urine. We know that it takes about 10 days for the drug HCG to clear from blood and urine. So if you do an HPT too soon (10 days or less after the HCG injection) you may get a false positive because you are detecting the medication that is still in your blood and urine, not the HCG that a pregnancy is making. On the other hand, if you do an HPT too soon after ovulation or egg retrieval, you may get a false negative because the level of HCG that the pregnancy is making may be too low for the kit to detect.

Most of the time, your doctor or nurse will give you a date for your pregnancy test that will give accurate results. And believe me, they really do know and appreciate how hard it is for you to wait 12 to 14 days to test. I would recommend that you not waste your money and POAS (pee on a stick) before your scheduled test. It’s tempting I know, but the results may not be accurate and could set you up for disappointment and confusion. Instead, why not spend that money on something nice for youreself like a manicure or a bouquet of flowers and leave the pregnancy test to the lab.

Do you have a questions for me? Ask it here! Perhaps I'll answer it in an upcoming "Ask a Fertility Nurse" column!


Gina Paoletti-Falcone, RN, BSN is a graduate of Northeastern University and has worked in Women’s Health since 1978. In 2004, Gina joined Freedom Fertility Pharmacy as the Clinical Educator responsible for developing infertility educational content for employees, patients, nurse, and managed care plans in print and online. Gina writes a fertility blog on the Freedom Fertility Pharmacy website and enjoys educating and empowering patients to take an active role in their fertility treatment.

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