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When to take a pregnancy test if the period is irregular?

By Mónica Aura Masip M.D., M.Sc. (gynecologist).
Last Update: 03/25/2022

Pregnancy tests detect the presence of the pregnancy hormone (HCG) in both blood and urine. HCG begins to be secreted by the trophectoderm of the embryo after implantation and passes into the blood and urine.

The concentrations of this hormone in urine are a little lower than in blood, especially in the first days of its possible detection, so if we perform a test too early it is easier to detect it in blood than in urine.

Nowadays there are very sensitive urine tests in pharmacies that detect already very low amounts of HCG around 12-25 IU of HCG. Even if a woman's cycle is irregular, HCG begins to be detected between 10 and 15 days after the possible conception, therefore, if it is known approximately when the possible conception occurred, the test can be performed about 15 days later.

 Mónica  Aura Masip
Mónica Aura Masip
M.D., M.Sc.
Gynecologist
Dr. Mónica Aura has a degree in Medicine and General Surgery from the Autonomous University of Barcelona (UAB). She is also a specialist in Gynecology and Obstetrics from the Hospital de Santa Creu y Sant Pau and has a Master's degree in Human Assisted Reproduction from the University Juan Carlos I of Madrid and another in Health Center Management from the UB.
Licence number: 31588
Gynecologist. Dr. Mónica Aura has a degree in Medicine and General Surgery from the Autonomous University of Barcelona (UAB). She is also a specialist in Gynecology and Obstetrics from the Hospital de Santa Creu y Sant Pau and has a Master's degree in Human Assisted Reproduction from the University Juan Carlos I of Madrid and another in Health Center Management from the UB. Licence number: 31588.