Fertility · Cycle Tracking

Luteal Phase — Length, Defect & Fertility

Second half of your cycle (ovulation to period). Normal 12-14 days. <10 days = luteal phase defect. How to track (BBT, OPK, progesterone test), treatment, fertility implications.

Last reviewed 2 June 2026

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Optional — gives an exact luteal phase

Luteal phase length

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Days past ovulation (DPO)

1 DPO

Counting from your ovulation date

Estimated next period

22 June 2026

If luteal phase ≈ 14 days

What does this mean?
Your luteal phase is the second half of your cycle — from ovulation to the day before your next period. It’s when the corpus luteum produces progesterone to prepare and maintain the uterine lining. A typical luteal phase is 12-16 days. Shorter than 10 days (luteal phase defect) can theoretically affect implantation — the embryo runs out of time before the lining sheds. One short cycle isn’t diagnostic; charting 3-6 cycles gives a clearer picture. Treatments (progesterone supplementation, clomid) are available if a true defect is confirmed.

Luteal phase length varies between cycles. One measurement is a data point, not a diagnosis. Charting several cycles gives a far more reliable picture. Medical disclaimer.

What is the luteal phase?

Second half of menstrual cycle — from ovulation to next period start. Normally 12-14 days. Corpus luteum produces progesterone, preparing uterine lining for pregnancy.

If pregnancy: hCG maintains corpus luteum until placenta takes over ~10 weeks. If not: corpus luteum dies, progesterone falls, period starts.

Normal length

  • 12-14 days typical (range 10-16).
  • <10 days: luteal phase defect (LPD).
  • >16 days: uncommon.

Consistent length typical for individual woman.

Short luteal phase (LPD)

Suggests corpus luteum not producing enough progesterone.

Possible causes:

  • Hormonal imbalance (PCOS, thyroid).
  • Low ovarian reserve.
  • Stress.
  • Recent pregnancy loss.
  • Perimenopause.

Higher early miscarriage risk; implantation difficulty.

How to measure

  1. Identify ovulation via BBT (temp rises 0.2-0.5°C), OPK (LH surge), cervical mucus, mid-cycle pain.
  2. Count days from ovulation to first day of next period.
  3. Track 3+ cycles to establish pattern.

Apps: Flo, Clue, Natural Cycles, Fertility Friend.

Progesterone test

7 days after ovulation (day 21 of 28-day cycle). >30 nmol/L (>10 ng/mL) suggests ovulation occurred. <16 nmol/L (5 ng/mL): probably no ovulation. Single test limited — pulsatile.

Treatment options

  • Stress reduction.
  • Weight optimisation.
  • Treat underlying issues (thyroid, PCOS).
  • Progesterone supplements — Cyclogest, Utrogestan vaginal; or oral micronised.
  • hCG injections sometimes post-ovulation.
  • Ovulation induction (letrozole, clomiphene) may help.

If trying to conceive

  • Sex every 1-2 days through fertile window.
  • Don’t time ovulation-only — sperm survives 5 days.
  • Folic acid, healthy weight, no smoking/alcohol.
  • Track cycle 2-3 months before targeting.
  • GP after 12 months (6 months if ≥35).

PCOS + luteal phase

Anovulation common in PCOS → no luteal phase. When ovulation does occur, often short or low progesterone. Treatment: ovulation induction (letrozole first-line); metformin; lifestyle; progesterone support.

After coming off pill

Ovulation returns within 1-2 cycles usually. Short luteal phases sometimes first few cycles post-pill — not permanent. Folic acid before trying.

Breastfeeding

No ovulation while exclusively breastfeeding (lactational amenorrhoea). First cycles often have short luteal phases; resolves with weaning.

Different scenarios

Scenario 1: 8-day luteal phase tracking

LPD pattern. Discuss with GP/fertility specialist. Progesterone test. Underlying causes workup.

Scenario 2: PCOS, irregular cycles, trying 9 months

Fertility specialist. Letrozole ovulation induction. Progesterone support post-ovulation.

Scenario 3: Just stopped pill, irregular for 3 months

Normal post-pill phase. Continue tracking. Most regulate by 3-6 months.

Scenario 4: 14-day consistent luteal phase, ovulation day 14, regular cycles

Normal. Useful baseline for conception timing.

Scenario 5: Perimenopause, cycles shortening

Often LPD-pattern. Fertility declining. Discuss with GP about timing if hoping to conceive.

Care guidance — luteal phase

  • Track 3+ cycles for pattern.
  • BBT, OPK, mucus monitoring tools.
  • Day 21 progesterone confirms ovulation.
  • LPD treatable if cause identified.
  • Don’t over-stress about one short cycle.
  • Healthy lifestyle supports cycle.
  • Fertility specialist for persistent issues.

Sources

  • NICE NG156. Fertility problems.
  • ASRM. Luteal phase deficiency: a committee opinion.
  • Teede HJ. 2023 International PCOS Guideline.

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Frequently asked questions

What is the luteal phase?
SECOND HALF of menstrual cycle — from OVULATION to next period start. NORMALLY 12-14 DAYS. Ovary forms CORPUS LUTEUM (yellow body) at site of released egg → produces PROGESTERONE (+ small estrogen). Progesterone PREPARES uterine lining for possible pregnancy. IF NO PREGNANCY: corpus luteum dies ~14 days after ovulation → progesterone falls → period starts. IF PREGNANCY: placenta produces hCG → maintains corpus luteum → progesterone continues until placenta takes over ~10 weeks.
How long should my luteal phase be?
NORMAL: 12-14 DAYS (range 10-16). SHORTER than 10 days = LUTEAL PHASE DEFECT (LPD). LONGER than 16 days uncommon. CONSISTENT LENGTH typical for individual woman; variation usually small. KNOWING your luteal phase length helps: (1) Estimate ovulation backward from period; (2) Identify possible fertility issues; (3) Time conception attempts.
What's a short luteal phase mean?
LUTEAL PHASE DEFECT (LPD) — <10 days. SUGGESTS: corpus luteum not producing enough progesterone or for long enough. CAUSES: hormonal imbalance (PCOS, thyroid), low ovarian reserve, stress, recent pregnancy loss, perimenopause. IMPLICATIONS: makes implantation difficult (uterine lining not optimally prepared); higher early miscarriage risk. NOT a definite cause of infertility — controversial as standalone diagnosis. EVALUATION + treatment in fertility context.
How do I know my luteal phase length?
(1) IDENTIFY OVULATION: BBT (basal body temperature) — temp rises 0.2-0.5°C at ovulation + stays raised through luteal phase; OPK (ovulation predictor kit) — detects LH surge ~24-36h before ovulation; cervical mucus changes (egg-white at ovulation); ovulation pain (mid-cycle). (2) COUNT DAYS from ovulation to first day of next period = luteal phase length. (3) TRACK FOR 3+ CYCLES to establish pattern. APP support: Flo, Clue, Natural Cycles, Fertility Friend.
Can luteal phase be treated?
TREATMENT depends on cause + context: (1) STRESS reduction; (2) WEIGHT optimisation (extremes affect cycle); (3) TREATING underlying issues (thyroid, PCOS); (4) PROGESTERONE SUPPLEMENTS — vaginal pessaries (Cyclogest, Utrogestan) or oral micronised progesterone; in fertility treatment cycles standard. (5) HCG INJECTIONS sometimes used post-ovulation. (6) OVULATION INDUCTION (letrozole, clomiphene) may help by stimulating better follicles. CONSULT fertility specialist if persistent + trying to conceive.
What progesterone level is normal?
MEASURED 7 DAYS AFTER OVULATION (day 21 of 28-day cycle, longer luteal phase elsewhere): >30 nmol/L (>10 ng/mL) suggests ovulation occurred. <16 nmol/L (5 ng/mL): probably no ovulation. CAN BE PULSATILE so single measurement limited. REPEAT testing useful. PROGESTERONE rises through luteal phase, peaks ~7 days post-ovulation, falls if no pregnancy. PRIVATE labs ~£30; NHS GP can request.
What's the difference between ovulation calculator + luteal phase tracker?
OVULATION CALCULATOR: predicts WHEN you'll ovulate (forward calculation from period). LUTEAL PHASE TRACKER: measures from OVULATION to PERIOD (backward). BOTH useful for fertility planning. KNOWING luteal phase length improves ovulation prediction: if cycle 30 days + luteal phase 13 days, ovulation = day 17 (cycle day). LONGER LUTEAL PHASE = ovulation later than midcycle.
Does PCOS affect luteal phase?
OFTEN. PCOS: ANOVULATION (no ovulation) common → no luteal phase. WHEN OVULATION DOES occur: luteal phase often SHORT or low progesterone. CAUSES: hormonal imbalance, irregular follicular development. TREATMENT: ovulation induction (letrozole first-line per PCOS-II trial — better than clomiphene); metformin; lifestyle; progesterone support. /calculators/pcos-pregnancy for context.
What if I'm trying to conceive?
OPTIMISE: (1) HAVING SEX every 1-2 DAYS through fertile window (5 days before + day of ovulation); (2) Avoid OVULATION-only timing (sperm survives 5 days + waiting until ovulation can miss window); (3) STANDARD preconception: folic acid 400mcg-5mg, healthy weight, smoking + alcohol cessation; (4) TRACK CYCLE 2-3 months before targeting; (5) AFTER 12 MONTHS no pregnancy (or 6 months if ≥35), see GP for fertility workup. (6) IF SHORT LUTEAL PHASE persistent: discuss with fertility specialist.
Can stress shorten luteal phase?
ACUTE OR CHRONIC STRESS may: (1) DELAY ovulation; (2) Affect luteal phase length (mild shortening sometimes); (3) Cause anovulation in severe stress. RESEARCH: equivocal — modest effects in most. MANAGEMENT: stress reduction (CBT, mindfulness, exercise, sleep, social support). DON'T BLAME yourself if fertility issues — STRESS = ONE FACTOR among many. ANXIETY about fertility creates feedback loop.
What about after coming off the pill?
OVULATION usually RETURNS within 1-2 cycles after stopping pill. SOME WOMEN take 3-6 months to regulate. SHORT LUTEAL PHASES sometimes occur first few cycles post-pill. NOT permanent. CAN start trying immediately if you want; cycles may be irregular initially. FERTILITY not impaired by previous pill use. FOLIC ACID 400mcg before trying. SOME women conceive in first ovulation back.
Does breastfeeding affect luteal phase?
BREASTFEEDING: usually NO OVULATION while exclusively breastfeeding (lactational amenorrhoea). RETURN of cycles: variable — sometimes within weeks of reducing feeds, sometimes months. FIRST cycles often have SHORT LUTEAL PHASES — corpus luteum function reduced. BREASTFEEDING-RELATED short luteal phase resolves with weaning typically. NOT necessarily indicative of long-term issue.
Can luteal phase change with age?
PERIMENOPAUSE (40s typically): luteal phase often shortens; cycles irregular; ANOVULATION more common. EGG QUALITY declines from ~35; reflected in luteal phase shortening sometimes. EARLY-MID 30s: usually preserved. POST-MENOPAUSE: no luteal phase (no ovulation). HRT can affect endogenous cycle perception in perimenopausal women still ovulating sporadically.
How does this relate to other calculators on BumpBites?
Companion: /calculators/ovulation; /calculators/fertility-window; /calculators/fertility-tracking-accuracy; /calculators/pcos-pregnancy; /calculators/endometrial-thickness; /calculators/semen-analysis; /calculators/conception-date; /calculators/pregnancy-test-timing.

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