What is the average decrease in ferritin (iron storage protein) levels during a woman's menstrual period?

Ferritin Decrease During Menstruation

Women lose approximately 0.3-0.5 mg of iron daily during menstruation, which can lead to a gradual depletion of ferritin levels over the menstrual cycle. 1

Iron Loss During Menstruation

• Women of childbearing age require additional iron to compensate for menstrual blood loss, which averages 0.3-0.5 mg daily during the childbearing years 1
• In healthy women with normal menses, the median value of iron lost per menstrual cycle is approximately 0.87 mg (range 0.102-2.569 mg) 2
• Women with menorrhagia (excessive menstrual bleeding) lose significantly more iron, with median values of 5.2 mg per cycle (range 1.634-8.665 mg) 2

Impact on Ferritin Levels

• Ferritin is the primary storage form of iron in the body, with 1 μg/L of serum ferritin equaling approximately 10 mg of stored iron 3
• Women have significantly lower average ferritin levels (43 μg/L) compared to men (135 μg/L), largely due to menstrual blood loss 3
• Women with normal menstruation typically have ferritin levels that fluctuate but remain within normal ranges, while those with heavy menstrual bleeding often develop depleted iron stores 2

Clinical Significance

• Among women with menorrhagia, mean serum ferritin levels can be significantly reduced to approximately 6.4 ng/mL (compared to 36.2 ng/mL in healthy women) 2
• A substantial proportion of women (40-60% depending on diet) may have low iron stores (serum ferritin <10 μg/L) due to menstrual blood loss 4
• Iron deficiency without anemia is common in menstruating women - in one study of young women with heavy menstrual bleeding, 50.9% had ferritin <20 ng/mL indicating iron deficiency, but only 41.4% of these iron-deficient women were anemic 5

Risk Factors for Greater Ferritin Decrease

• Heavy menstrual blood loss (>80 mL/month) affects approximately 10% of women of childbearing age and is a significant risk factor for iron deficiency anemia 1
• Use of an intrauterine device is associated with increased menstrual blood loss and consequently greater iron loss 1
• Diet plays a significant role - women consuming poultry/fish diets tend to have higher ferritin levels than those on lacto-ovo-vegetarian diets 4
• Being overweight or obese is associated with significantly higher odds of having iron deficiency (odds ratio 2.81) compared to normal BMI 5

Implications for Iron Requirements

• Due to menstrual losses, adult menstruating women require approximately 2.84 mg/day of absorbed iron, while teenage menstruating women require about 3.21 mg/day 6
• When accounting for dietary iron bioavailability (approximately 15% in Western diets), the dietary iron requirements increase to 18.9 mg/day for adult menstruating women and 21.4 mg/day for teenage menstruating women 6
• Only about one-fourth of adolescent girls and women of childbearing age (12-49 years) meet the recommended dietary allowance for iron through diet alone 1

Clinical Monitoring Considerations

• Screening for iron deficiency with hemoglobin or complete blood count alone misses more than half of iron deficiency cases in women with heavy menstrual bleeding 5
• Measuring ferritin levels is recommended for at-risk patients to allow for earlier implementation of iron therapy 5
• Serum ferritin levels <15 μg/L are highly specific for iron deficiency, while levels <30 μg/L generally indicate low body iron stores 3