What cycle day do you ovulate?
People who have regular cycles presumably ovulate every month at a predictable time. In a typical 28-day cycle, it takes about 14 days to grow and develop a dominant follicle. If you are monitoring for ovulation, the leutenizing hormone (LH) surge comes roughly 24 to 44 hours before ovulation.
In a 28-day cycle, ovulation of the oocyte (or egg) occurs around day 14. The luteal phase starts once the follicle releases the oocyte, and generally lasts for 14 days. The area of ovulation on the ovary changes to form the "corpus luteum," which secretes progesterone.
Ovulation can be confirmed after it has occurred by testing estrogen and progesterone hormone levels via bloodwork.
The Importance of Progesterone
Progesterone is a vital part of the conception process. It changes the uterine lining into its secretory phase, making the uterine lining receptive and hospitable to the implantation of an embryo.
Without implantation of an embryo, the corpus luteum and its secretion of progesterone will recede within 14 days. Once ovulation has occurred, your menses (or period) should begin about 14 days later.
As you can see, Day 21 is meant to be a marker for when you're in the middle of the luteal phase of your cycle, and when progesterone production is at its peak.
If your reproductive endocrinologist is concerned about whether your luteal phase is adequate, (i.e. whether the corpus luteum makes enough progesterone to support a healthy secretory endometrium and implantation of an embryo), they may check your progesterone level on "Day 21," at the luteal phase peak.
If your reproductive endocrinologist is concerned that you may not be ovulating at all, "Day 21" is also a good day to check progesterone levels, as a level above 5 ng/ml will confirm that ovulation has taken place.
What are normal progesterone levels in women?
If your progesterone level is high (above 5 ng/ml) this confirms that you have indeed ovulated and entered the luteal phase, the second half of the menstrual cycle.
Progesterone rises after ovulation, reaching a peak around Day 21 of a 28-day cycle. Peak luteal phase progesterone levels can vary from cycle to cycle, and from person to person.
Ideally, “Day 21” peak luteal progesterone levels should be 10ng/ml or higher.
What if my hormone levels are low?
If your fertility specialist is concerned that you are not ovulating, or that your progesterone or estrogen levels might be too low to support a lining conducive to implantation, not to worry!
Note: There are many options to boost these hormone levels and make a receptive endometrium (uterine lining). Your doctor will help you get your levels where they need to be so you can have the best chance at a healthy pregnancy!
Progesterone levels can be supplemented with vaginal or injectable progesterone supplements. Estradiol levels can be supplemented with oral, vaginal or transdermal estrogen.
Your fertility specialist may also check your peak luteal progesterone and estrogen levels during a treatment cycle. For certain treatments, such as in vitro fertilization (IVF), we recommend estrogen and progesterone supplementation in the luteal phase to most of our patients to boost hormone levels and ensure the best chances of embryo implantation.
In ovulation induction and natural cycles, we typically only supplement if we check your estrogen and progesterone levels and have found them to be too low in the luteal phase of the cycle.
What are the effects of low progesterone?
Low progesterone levels can affect both the menstrual cycle and a person's overall fertility, since progesterone helps create a good environment for a pregnancy to develop. When progesterone levels are low, it’s harder for an embryo to implant and grow.
Low levels of progesterone can also contribute to:
- absence of menstruation
- poor ovarian function
What if I don't ovulate on my own?
If you rarely or never get your menses (i.e. have a period), it means that you may be ovulating very rarely, or you may not ovulate on your own at all, which means that your natural "Day 21" progesterone levels can’t be checked.
If you are not ovulating or are rarely ovulating, your doctor will prescribe medication to induce ovulation. The following are some commonly used medications:
- Clomiphene citrate (i.e. Clomid)
- Injectables (like Ovidrel, HCG, or FSH)
Once ovulation has occurred in a treatment cycle, we can then assess your peak progesterone levels to confirm ovulation and whether your luteal progesterone and estrogen levels are adequate to support a healthy embryo implantation.
Success Begins With Knowledge
Fertility assessments like Day 21 testing give you and your medical team the very best chance at achieving fertility treatment success. No matter which treatment path you're on, Day 21 fertility testing is a vital step in understanding your cycles, hormone fluctuations, and determining the best course of treatment for you.
If you're just getting started on your fertility journey, be sure to check out our comprehensive guide to your first consultation and download your free worksheet.
We wish you all the best on your journey to baby!