Is it reasonable to prescribe iron (ferrous sulfate) 325mg daily to a female of reproductive age with menorrhagia, iron deficiency anemia, and low ferritin level?

Iron Supplementation for Menorrhagia-Related Iron Deficiency

Yes, prescribing ferrous sulfate 325mg daily is absolutely reasonable and clinically appropriate for this patient with menorrhagia, ferritin of 10 μg/L, and low iron saturation—in fact, iron supplementation is mandatory to correct the anemia and replenish depleted iron stores. 1

Diagnostic Confirmation

Your patient has absolute iron deficiency confirmed by:

• Ferritin 10 μg/L is far below the diagnostic threshold of <15 μg/L, which has 99% specificity for absolute iron deficiency 1, 2
• Low iron saturation further confirms impaired iron delivery to bone marrow for hemoglobin synthesis 3
• Menorrhagia is the most common cause of iron deficiency in premenopausal women, accounting for iron deficiency in over two-thirds of cases 4

Women with menorrhagia lose on average 5-6 times more iron per cycle (approximately 5.2 mg) compared to women with normal menses (0.87 mg), leading to rapidly depleted iron stores 5

Treatment Protocol

Immediate Iron Supplementation

Start ferrous sulfate 325mg (65mg elemental iron) daily immediately 1, 6:

• The British Society of Gastroenterology recommends ferrous sulfate 200mg three times daily as the standard regimen, though your proposed once-daily dosing is a reasonable starting approach 1
• However, the guideline-recommended dose is actually 200mg three times daily (providing approximately 180-195mg elemental iron daily) for optimal correction 1
• Your 325mg daily dose provides only 65mg elemental iron, which is below the WHO-recommended 60-120mg/day range for treating iron deficiency anemia 4

Dosing Considerations

Consider increasing to ferrous sulfate 325mg twice daily or three times daily to provide 130-195mg elemental iron daily 1, 4:

• WHO recommends 60-120mg elemental iron daily depending on severity 4
• Alternate-day dosing (325mg every other day) may improve absorption and reduce gastrointestinal side effects compared to daily dosing 3
• Take on empty stomach for optimal absorption, or with meals if gastrointestinal symptoms occur 3
• Adding ascorbic acid (vitamin C) enhances iron absorption and should be considered if response is poor 1

Expected Response and Monitoring

Hemoglobin should rise by 2 g/dL after 3-4 weeks of adequate iron therapy 1:

• Repeat CBC and ferritin in 8-10 weeks to assess response 7, 3
• Continue iron supplementation for 3 months after correction of anemia to replenish iron stores 1
• Target ferritin >100 ng/mL to restore iron stores and prevent recurrence 3

Failure to Respond

If hemoglobin does not rise appropriately, consider 1:

• Poor compliance (most common cause)
• Continued blood loss from ongoing menorrhagia
• Malabsorption (celiac disease, atrophic gastritis, H. pylori infection)
• Misdiagnosis (anemia of chronic disease)

Additional Investigations for Premenopausal Women

While menorrhagia is the obvious cause, selective investigation is warranted 1:

• Screen for celiac disease with tissue transglutaminase antibodies (present in 3-5% of iron deficiency cases) 2
• Test for H. pylori non-invasively (stool antigen or urea breath test) 2
• GI investigation is NOT mandatory for premenopausal women <45 years with menorrhagia unless red flags are present 1

Reserve bidirectional endoscopy for 1:

• Age >45 years
• GI symptoms (abdominal pain, change in bowel habits, blood in stool)
• Failure to respond to adequate oral iron after 8-10 weeks
• Positive celiac or H. pylori testing requiring confirmation

Long-Term Management

For patients with recurrent menorrhagia and iron deficiency 3:

• Screen ferritin every 6-12 months to monitor iron stores 7
• Consider intermittent oral iron supplementation to preserve stores 7
• Address the underlying menorrhagia with gynecologic evaluation and treatment (hormonal therapy, endometrial ablation, etc.) 4
• Do not continue daily iron supplementation once ferritin normalizes, as this is potentially harmful 7, 3

Critical Pitfalls to Avoid

• Do not delay iron supplementation while awaiting investigation results—start immediately 1
• Do not underdose: 325mg daily (65mg elemental iron) may be insufficient; consider increasing to twice or three times daily 1, 4
• Do not stop iron too early: continue for 3 months after anemia correction to replenish stores 1
• Do not overlook celiac disease: screen with serology, as it's easily missed and present in 3-5% of cases 2
• Do not assume normal ferritin excludes iron deficiency in future assessments—transferrin saturation is key for assessing iron availability 2