The essentials

The luteal phase is the part of your cycle between ovulation and your next period. It usually lasts 12 to 14 days, and 11 to 17 days is still normal. A luteal phase of 10 days or less is called short; one short cycle is common and does not mean infertility. You find your own length by pinpointing ovulation with LH strips or a temperature chart, then counting the days to your period.

What can a blood test show about your luteal phase?

No blood test measures the luteal phase itself, but a progesterone level drawn in its middle shows whether you ovulated. Below, a fictitious US report for a sample taken 7 days after a positive ovulation (LH) test.

Fictitious example of a lab report line (United States format)
TestResultReference rangeFlag
Progesterone11.2 ng/mLFemale: follicular phase 0.1-0.9; ovulatory phase 0.1-12.0; luteal phase 1.8-23.9-
  1. Reference range: one range per phase, here from Labcorp[7]. There is no flag because the lab does not know your cycle day.
  2. Result: a luteal value above 3 ng/mL is presumptive evidence of recent ovulation, according to the American Society for Reproductive Medicine (ASRM)[2]. 11.2 ng/mL fits an ovulatory cycle.
  3. Timing: progesterone peaks 6 to 8 days after ovulation and swings between about 5 and 40 ng/mL within hours, so one value says little about luteal "strength"[2].

Unsure what your hormone results say about your cycle? BloodSense reads your whole report in context and helps you prepare questions for your next visit.

Get my hormone results explained

In a 28-day cycle, that peak falls around day 21, which is where the "day 21" test gets its name. Ranges, units and low or high values are covered in our guide to progesterone test results.

What is the luteal phase?

In the first half of the cycle (follicular phase), a follicle grows in the ovary. A surge of luteinizing hormone (LH) then triggers ovulation; the LH rise begins about 36 hours before the egg is released[1]. The empty follicle turns into the corpus luteum, a temporary gland that makes progesterone and some estrogen[2].

Progesterone prepares the lining of the uterus for an embryo. If pregnancy starts, the embryo's hCG hormone keeps the corpus luteum working; without hCG it fades, progesterone falls and your period starts[2].

How long is the luteal phase?

It is steadier than the first half of the cycle, but not always 14 days.

Luteal phase length in published data (days)
MeasureDaysSource
Typical length12-14 (range 11-17)ASRM 2026[2]
Mean in 612,613 app-tracked cycles12.4 (95% of cycles 7-17)Bull 2019[3]
Mean in 1,635 cycles of women trying to conceive14Crawford 2017[4]
Time from ovulation to the next period7 to 19US Office on Women's Health[1]
Short luteal phase (classic definition)10 or fewerASRM 2026[2]

Most of the difference between a 26-day and a 34-day cycle comes from the timing of ovulation, in the follicular phase[3]. In the large app study, cycle length and follicular phase shortened with age from 25 to 45, while the luteal phase changed little[3].

How do I calculate my luteal phase?

Count from the day after ovulation to the day before your next period. The hard part is finding ovulation:

  • Urine LH strips: a positive test predicts ovulation within about 48 hours[6]. Count ovulation as the day after your first positive strip.
  • Basal body temperature (BBT): taken on waking, it rises 0.5 to 1.0°F after ovulation because of progesterone and stays up until just before your period[6]. It confirms ovulation after the fact.
  • Calendar only: subtracting 14 from your cycle length is a guess.

Example: positive LH strip on day 14, ovulation day 15, period on day 29. Days 16 to 28 make a 13-day luteal phase. Track several cycles, noting the first day of each period (your LMP, last menstrual period).

What causes a short luteal phase?

Many cases have no illness behind them[2].

  • Common An occasional short cycle: in regularly menstruating women, 8.9% of ovulatory cycles had a luteal phase under 10 days, and only 3.4% of women had it twice[5].
  • Common Intense exercise, eating too little, weight loss or stress[2]: in one study, 43% of cycles in recreational runners showed a luteal phase deficiency, while 90% of cycles in sedentary women were ovulatory[11].
  • Possible Thyroid disease or high prolactin: both can disturb the brain signals to the ovary[2]. Doctors check TSH and prolactin levels.
  • Possible PCOS, endometriosis, obesity or late reproductive age: all are linked with luteal changes[2]. See PCOS symptoms and tests and perimenopause hormone tests.
  • Possible Smoking: women with a short luteal phase were more often smokers[4].
  • Rare Untreated 21-hydroxylase deficiency: an adrenal enzyme condition[2], screened with 17-OH progesterone.

A "long" luteal phase usually means ovulation happened later than you thought, or that you are pregnant: take a pregnancy test if your period is late.

Does a short luteal phase affect fertility?

Less than often claimed. In a study of 284 women aged 30 to 44 trying to conceive, 18% of cycles had a luteal phase of 11 days or less. Right after a short cycle, the odds of pregnancy in the next cycle were 0.82 times those of other women, but after 12 months the chance of pregnancy was no different[4].

The ASRM 2026 committee opinion states that luteal phase deficiency (also called luteal phase defect) has not been proven to cause infertility or recurrent miscarriage on its own. No test reliably separates fertile from infertile women, so neither progesterone measurements nor endometrial biopsy can be recommended to diagnose it[2]. The first step is to treat an underlying cause, such as a thyroid or prolactin problem[2].

What are luteal phase symptoms?

Rising then falling progesterone explains a slightly higher morning temperature[6] and, for many, premenstrual symptoms such as bloating, breast tenderness, headaches, mood changes or tiredness[1][9].

The American College of Obstetricians and Gynecologists (ACOG) diagnoses premenstrual syndrome (PMS) when symptoms appear in the 5 days before a period for at least three cycles in a row, end within 4 days after bleeding starts and interfere with daily life. Severe mood symptoms may be premenstrual dysphoric disorder (PMDD)[9]. ACOG's guideline reviews lifestyle measures, counseling and medicines, often combined[10].

What can make luteal phase tracking or testing misleading?

  • Fever, alcohol, poor sleep, a changed waking time or recently stopping the pill can shift your temperature chart[6].
  • An LH surge does not always lead to ovulation; this happened in 4.3% of women in one study[6].
  • Hormonal birth control stops the natural cycle, so there is no luteal phase to measure.
  • One short cycle is not a pattern: chart several cycles[5].
  • For a progesterone test, note your LMP and the day of your positive LH test[8]. Practical tips are in our guide to what to expect at a blood draw.

When should I see a doctor about my luteal phase?

When to see a doctor

  • Emergency: call 911 for severe one-sided belly pain, fainting or heavy bleeding when you could be pregnant. For thoughts of self-harm before your period, call or text 988.
  • Within 24 to 48 hours for bleeding or cramps with a positive pregnancy test.
  • At your next appointment if your luteal phase is 10 days or less in several cycles, you spot for days before each period, PMS disrupts your life, or you have tried to conceive for 12 months (6 months if you are 35 or older)[12].

Questions to ask your doctor

  1. Do my charts show that I ovulate, and how long is my luteal phase?
  2. Should my thyroid, prolactin or other hormones be checked?
  3. On which day should my progesterone be drawn, given my cycle length?

Frequently asked questions

Can you get pregnant during the luteal phase?

Only at its very start. The egg lives 12 to 24 hours after ovulation, so the fertile days are mostly the ones before it[1].

Do FSH and estradiol matter for the luteal phase?

Yes. A short luteal phase has been linked with lower follicular estradiol and lower LH and FSH levels[5]. Your estradiol result is read with your cycle day.

Should I take progesterone to lengthen my luteal phase?

Not on your own. In natural cycles, progesterone has not been shown to improve pregnancy rates, and in women with recurrent miscarriage who conceived naturally, a large trial found no reduction in miscarriage[2].

  1. US Department of Health and Human Services, Office on Women's Health. Your menstrual cycle. womenshealth.gov (accessed November 8, 2026)
  2. Practice Committee of the American Society for Reproductive Medicine. Diagnosis and treatment of luteal phase deficiency: a Committee Opinion. Fertil Steril. 2026;126(4):633-639. doi:10.1016/j.fertnstert.2026.06.014; full text: asrm.org (accessed November 8, 2026)
  3. Bull JR, Rowland SP, Scherwitzl EB, Scherwitzl R, Danielsson KG, Harper J. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ Digit Med. 2019;2:83. doi:10.1038/s41746-019-0152-7 (accessed November 8, 2026)
  4. Crawford NM, Pritchard DA, Herring AH, Steiner AZ. Prospective evaluation of luteal phase length and natural fertility. Fertil Steril. 2017;107(3):749-755. doi:10.1016/j.fertnstert.2016.11.022 (accessed November 8, 2026)
  5. Schliep KC, Mumford SL, Hammoud AO, et al. Luteal phase deficiency in regularly menstruating women: prevalence and overlap in identification based on clinical and biochemical diagnostic criteria. J Clin Endocrinol Metab. 2014;99(6):E1007-E1014. doi:10.1210/jc.2013-3534 (accessed November 8, 2026)
  6. Su HW, Yi YC, Wei TY, Chang TC, Cheng CM. Detection of ovulation, a review of currently available methods. Bioeng Transl Med. 2017;2(3):238-246. doi:10.1002/btm2.10058 (accessed November 8, 2026)
  7. Labcorp. Progesterone (test 004317). labcorp.com (accessed November 8, 2026)
  8. MedlinePlus. Progesterone Test. US National Library of Medicine. medlineplus.gov (accessed November 8, 2026)
  9. American College of Obstetricians and Gynecologists. Premenstrual Syndrome (PMS). acog.org (accessed November 8, 2026)
  10. American College of Obstetricians and Gynecologists. Management of Premenstrual Disorders: ACOG Clinical Practice Guideline No. 7. Obstet Gynecol. 2023;142(6):1516-1533. doi:10.1097/AOG.0000000000005426 (accessed November 8, 2026)
  11. De Souza MJ, Miller BE, Loucks AB, et al. High frequency of luteal phase deficiency and anovulation in recreational women runners. J Clin Endocrinol Metab. 1998;83(12):4220-4232. doi:10.1210/jcem.83.12.5334 (accessed November 8, 2026)
  12. US Department of Health and Human Services, Office on Women's Health. Infertility. womenshealth.gov (accessed November 8, 2026)

This page is general information. It does not replace the advice of a doctor, who interprets your cycle charts and results with your history and examination.