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FSH levels through the menstrual cycle

Follicle-stimulating hormone, from the pituitary gland, which grows each cycle’s wave of follicles. Below are the median and the 5th to 95th percentile for each day from 15 days before the LH peak to 14 after, in mIU/mL, which is the same number in IU/L.

What is a normal FSH level in the early follicular phase?

Across days −15 to −6 before the LH peak, the pooled median FSH in Stricker and colleagues’ 20 women was 6.42 mIU/mL (6.42 IU/L). Daily medians in that window ran from 4.59 to 6.88 mIU/mL, and FSH peaked with LH, at 12.82 mIU/mL on the day of the LH peak.

FSH through the menstrual cycle, daily median and 5th to 95th percentile Line chart of the daily median FSH in mIU/mL, with a band from the 5th to the 95th percentile, from day −15 to day +14 about the LH peak. The median peaks at 12.82 mIU/mL on day 0. Every value is in the table below. 05101520 −15−10−50+5+10+14 Days from the LH peak mIU/mL Follicular phaseLuteal phase LH peak Peak median 12.82 mIU/mL, day 0 Day −15: median 4.59 mIU/mL, 5th to 95th percentile 1.95 to 5.86 mIU/mL, 9 women Day −14: median 6.45 mIU/mL, 5th to 95th percentile 2.79 to 8.15 mIU/mL, 12 women Day −13 (day 1 of a 28-day cycle): median 6.34 mIU/mL, 5th to 95th percentile 4.24 to 7.79 mIU/mL, 14 women Day −12 (day 2 of a 28-day cycle): median 6.26 mIU/mL, 5th to 95th percentile 4.62 to 7.93 mIU/mL, 17 women Day −11 (day 3 of a 28-day cycle): median 6.61 mIU/mL, 5th to 95th percentile 5.50 to 9.01 mIU/mL, 19 women Day −10 (day 4 of a 28-day cycle): median 6.88 mIU/mL, 5th to 95th percentile 5.40 to 10.25 mIU/mL, 20 women Day −9 (day 5 of a 28-day cycle): median 6.65 mIU/mL, 5th to 95th percentile 5.04 to 8.80 mIU/mL, 20 women Day −8 (day 6 of a 28-day cycle): median 6.46 mIU/mL, 5th to 95th percentile 4.97 to 9.53 mIU/mL, 20 women Day −7 (day 7 of a 28-day cycle): median 6.63 mIU/mL, 5th to 95th percentile 4.66 to 8.59 mIU/mL, 20 women Day −6 (day 8 of a 28-day cycle): median 5.65 mIU/mL, 5th to 95th percentile 4.41 to 8.10 mIU/mL, 20 women Day −5 (day 9 of a 28-day cycle): median 5.45 mIU/mL, 5th to 95th percentile 4.19 to 7.33 mIU/mL, 20 women Day −4 (day 10 of a 28-day cycle): median 4.59 mIU/mL, 5th to 95th percentile 3.83 to 6.33 mIU/mL, 20 women Day −3 (day 11 of a 28-day cycle): median 4.35 mIU/mL, 5th to 95th percentile 3.55 to 6.62 mIU/mL, 20 women Day −2 (day 12 of a 28-day cycle): median 4.32 mIU/mL, 5th to 95th percentile 2.95 to 5.71 mIU/mL, 20 women Day −1 (day 13 of a 28-day cycle): median 5.15 mIU/mL, 5th to 95th percentile 3.20 to 8.56 mIU/mL, 20 women Day 0 (day 14 of a 28-day cycle): median 12.82 mIU/mL, 5th to 95th percentile 5.30 to 15.07 mIU/mL, 20 women Day +1 (day 15 of a 28-day cycle): median 8.01 mIU/mL, 5th to 95th percentile 5.20 to 15.43 mIU/mL, 20 women Day +2 (day 16 of a 28-day cycle): median 5.19 mIU/mL, 5th to 95th percentile 3.78 to 9.51 mIU/mL, 19 women Day +3 (day 17 of a 28-day cycle): median 4.73 mIU/mL, 5th to 95th percentile 3.05 to 8.18 mIU/mL, 20 women Day +4 (day 18 of a 28-day cycle): median 4.36 mIU/mL, 5th to 95th percentile 2.71 to 7.10 mIU/mL, 20 women Day +5 (day 19 of a 28-day cycle): median 3.88 mIU/mL, 5th to 95th percentile 2.22 to 5.97 mIU/mL, 20 women Day +6 (day 20 of a 28-day cycle): median 3.34 mIU/mL, 5th to 95th percentile 2.01 to 5.53 mIU/mL, 19 women Day +7 (day 21 of a 28-day cycle): median 3.31 mIU/mL, 5th to 95th percentile 1.47 to 5.34 mIU/mL, 20 women Day +8 (day 22 of a 28-day cycle): median 2.97 mIU/mL, 5th to 95th percentile 1.53 to 4.88 mIU/mL, 20 women Day +9 (day 23 of a 28-day cycle): median 2.73 mIU/mL, 5th to 95th percentile 1.26 to 4.09 mIU/mL, 20 women Day +10 (day 24 of a 28-day cycle): median 2.55 mIU/mL, 5th to 95th percentile 1.12 to 3.57 mIU/mL, 19 women Day +11 (day 25 of a 28-day cycle): median 2.54 mIU/mL, 5th to 95th percentile 1.09 to 3.26 mIU/mL, 20 women Day +12 (day 26 of a 28-day cycle): median 3.08 mIU/mL, 5th to 95th percentile 1.13 to 4.37 mIU/mL, 20 women Day +13 (day 27 of a 28-day cycle): median 3.73 mIU/mL, 5th to 95th percentile 1.55 to 7.58 mIU/mL, 16 women Day +14 (day 28 of a 28-day cycle): median 3.81 mIU/mL, 5th to 95th percentile 1.54 to 5.78 mIU/mL, 8 women
Median 5th to 95th percentile FSH in mIU/mL or IU/L, by day from the LH peak. Point at a day to read its figures; the table below lists every value.

FSH in each phase of the cycle

Pooled median FSH in each phase, Stricker and colleagues (2006), Table 2
Phase Days from the LH peak Median, mIU/mL or IU/L
Early follicular Days −15 to −6 6.42
Late follicular Days −5 to −1 4.66
LH peak Day 0 12.82
Early luteal Days +1 to +4 5.62
Mid-luteal Days +5 to +9 3.14
Late luteal Days +10 to +14 2.85

Each phase figure is the median of every sample taken in that phase, pooled, which is why it is not the median of the daily medians.

FSH on every day of the cycle

The second column places each day in a 28-day cycle with the LH peak on day 14, the textbook timing. Days −15 and −14 have no place in such a cycle, so it is blank for them.

Daily median, 5th and 95th percentile FSH, Stricker and colleagues (2006), Table 1
Day from the LH peak Day of a 28-day cycle Women mIU/mL or IU/L
Median 5th 95th
−15 9 4.59 1.95 5.86
−14 12 6.45 2.79 8.15
−13 1 14 6.34 4.24 7.79
−12 2 17 6.26 4.62 7.93
−11 3 19 6.61 5.50 9.01
−10 4 20 6.88 5.40 10.25
−9 5 20 6.65 5.04 8.80
−8 6 20 6.46 4.97 9.53
−7 7 20 6.63 4.66 8.59
−6 8 20 5.65 4.41 8.10
−5 9 20 5.45 4.19 7.33
−4 10 20 4.59 3.83 6.33
−3 11 20 4.35 3.55 6.62
−2 12 20 4.32 2.95 5.71
−1 13 20 5.15 3.20 8.56
0 14 20 12.82 5.30 15.07
+1 15 20 8.01 5.20 15.43
+2 16 19 5.19 3.78 9.51
+3 17 20 4.73 3.05 8.18
+4 18 20 4.36 2.71 7.10
+5 19 20 3.88 2.22 5.97
+6 20 19 3.34 2.01 5.53
+7 21 20 3.31 1.47 5.34
+8 22 20 2.97 1.53 4.88
+9 23 20 2.73 1.26 4.09
+10 24 19 2.55 1.12 3.57
+11 25 20 2.54 1.09 3.26
+12 26 20 3.08 1.13 4.37
+13 27 16 3.73 1.55 7.58
+14 28 8 3.81 1.54 5.78

All 20 women were sampled on 20 of the 30 days. The ends of the table rest on fewer, 9 on day −15 and 8 on day +14, because cycles differ in length. With 20 women or fewer on a day, each percentile is set by the one or two most extreme values.

How FSH moves through the cycle

FSH falls as estradiol rises in the late follicular phase: from day −5 to day −2 the FSH median drops every day, from 5.45 to 4.32 mIU/mL, while the estradiol median climbs from 71.4 to 177.3 pg/mL.

At the surge the FSH median grows 2.97-fold from day −2 to day 0, against 5.87-fold for LH over the same two days.

Through the luteal phase the median falls to 2.54 mIU/mL on day +11, the lowest in the table, then climbs every day to 3.81 on day +14, the start of the rise that recruits the next cycle’s follicles.

Day 3 of a 28-day cycle, the day an FSH test is often booked for, is day −11 on this table if the LH peak falls on day 14. There the median was 6.61 mIU/mL and the middle 90 percent ran from 5.50 to 9.01.

The menstrual cycle hormone simulator joins these medians into curves and plays FSH against the other three hormones, with the follicle and the lining drawn day by day.

Converting between units

An international unit measures biological activity against a WHO reference preparation rather than a mass, so FSH has no molar mass to convert with, and needs none: a milli-international unit per milliliter scales the unit and the volume by the same thousand, so mIU/mL and IU/L carry the same number.

mIU/mL to IU/L

  1. 1 mIU/mL = 0.001 IU ÷ 0.001 L
  2. = 1 IU/L

Where the numbers come from

Stricker and colleagues (2006) took blood from 20 women aged 20 to 36, with normal cycles and no hormonal contraception, on every day of one cycle, and measured FSH on an Abbott ARCHITECT analyzer in one laboratory. Each woman’s days are counted from her own LH peak, day 0, and each figure is the median of the women sampled that day.

The tables were read from the authors’ own copy of the paper, and every figure was checked against the independent transcription behind Häggström’s reference range charts.

See also

Source: Stricker R and colleagues, “Establishment of detailed reference values for luteinizing hormone, follicle stimulating hormone, estradiol, and progesterone during different phases of the menstrual cycle on the Abbott ARCHITECT analyzer”, Clin Chem Lab Med 2006;44(7):883-887.

The values are facts and free to use; this table’s selection and presentation are © 2026 ScienceQuest.