Peak +7 Progesterone (P+7)

Peak +7 Progesterone (P+7) is a blood test that measures progesterone about one week after ovulation. It is the main progesterone test in NaProTechnology. The blood draw is timed to the seventh day after the Creighton Model FertilityCare System (CrMS) Peak Day. That day falls in the strong part of the luteal phase, the second half of the cycle. Ovulation leaves behind a small gland, the corpus luteum, and that gland produces the progesterone.

Progesterone rises after ovulation and remains high through the middle of the luteal phase. The value on this day is not always the highest value of the cycle. In some cycles, the highest value comes a few days later, and the timing varies from cycle to cycle. The draw still falls within the strong part of the window, so it shows how well the corpus luteum is functioning. Clinicians compare the value with reference ranges built from normal ovulatory cycles. A low result can indicate luteal phase deficiency. The treating clinician interprets it with the rest of the luteal hormone results, never in isolation.

This cycle-timed approach distinguishes RRM hormone testing from a single random progesterone draw. A draw tied to a known point in the cycle can be compared with the reference ranges for that point. A random draw cannot be read with the same precision.