What Are The Chances Of A False Positive Ovulation Predictor Test If I Am Taking Clomid?



Ovulation Predictor Kits (OPK’s) are an important tool that many women who are trying to conceive choose to use to help determine when the best time for conception is.  An OPK detects a surge in the Luteinizing hormone (LH) that occurs when ovulation is about to take place. LH is released by the pituitary gland and is always in the bloodstream in small amounts. Its job is to stimulate the ovaries into producing and releasing eggs. The LH indicates that ovulation will happen in about 24 to 36 hours. The day the LH surge is detected and the day after are the most likely time for conception to occur.

Clomid is trade name of the medication Clomiphene citrate.  Clomid is a hormone that tricks the pituitary gland into producing more of the hormones FSH and LH.  FSH and LH, in turn, stimulate the ovary.  Clomid is typically taken in doses from 59 mg to 200 mg, and taken for 5-9 days.  Clomid is among the most inexpensive of available fertility drugs.  It is easily taken (orally rather than by injection) and it is the first line drug used for ovulation induction in patients with PCOS and other ovulatory disorders.

However, Clomid is a potent and complicated medication.  Clomid reacts with all of the tissues in the body that have estrogen receptors, such as the hypothalamus, pituitary, ovary, endometrium, vagina, and cervix.  Clomid influences the way that the four hormones required for ovulation, GnRH, FSH, LH and estradiol, relate and interrelate.  While we do not completely understand the mechanisms by which this drug works, in essence it appears that Clomid fools the body into believing that the estrogen level is low. This altered feedback information causes the hypothalamus (an area of the brain) to make and release more gonadotropin releasing hormone (GnRH) which in turn causes the pituitary to make and release more FSH and LH.  More follicle stimulating hormone and more luteinizing hormone should result in ovulation – the release of one or more mature eggs.





It is possible for Clomid to cause an OPK to register a false positive result.  This is most likely to happen if the OPK is used too soon after finishing the prescription for Clomid.  OPK manufacturers recommend that you should wait at least three days after stopping Clomid before using an OPK.  Thus, if you take Clomid on days 3-7 of your cycle, you can begin to use the OPK on day 10.  If you take Clomid on days 5-9, then you should wait until day 12 to use the OPK.  Because Clomid causes the release of LH into the bloodstream, the ovulation predictor test will detect this LH.  This can provide you with a false positive result, when you are not actually ovulating.


Last modified: February 10, 2013