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Answer · biomarkers

What causes low ferritin?

Short answer

Low ferritin is caused by chronic loss exceeding intake: menstruation, GI bleeding, malabsorption (celiac, H. pylori, gastric surgery), pregnancy demand, endurance training, and inadequate dietary iron. The cause must be identified before sustained repletion.

Reviewed by Dr. Laura PurdyMay 29, 2026

Full answer

Ferritin falls when ongoing iron loss or demand exceeds dietary intake and absorption. The most common drivers are menstruation (particularly heavy menses), occult gastrointestinal blood loss (peptic ulcer disease, colonic pathology), malabsorption from celiac disease, H. pylori infection, atrophic gastritis or post-bariatric anatomy, pregnancy and lactation demand, endurance training (footstrike hemolysis, GI losses, inflammatory hepcidin shifts), strict plant-based eating without sufficient iron-rich planning, and frequent blood donation. Identifying the cause matters: repleting iron without addressing an unrecognized GI source is incomplete care. Provider review reads ferritin alongside iron, TIBC, transferrin saturation, hemoglobin, and clinical history before recommending oral, IV, or dietary repletion.

Educational. Not a substitute for individualized provider review.

References & sources
  • Ferritin — Primary source · oMeds
  • Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29

Related answers

What is ferritin?
Ferritin is the body's primary iron storage protein. Low ferritin signals iron depletion — even before hemoglobin falls — and is implicated in fatigue, hair loss, and restless sleep. Ferritin is also an acute-phase reactant and can rise with inflammation.
Can low ferritin cause hair loss?
Yes. Low ferritin is a well-documented contributor to telogen effluvium (diffuse shedding) and worsens androgenetic alopecia. Many dermatologists target ferritin ≥40–70 ng/mL in active hair loss, even when CBC and hemoglobin are normal.
Ferritin vs iron?
Ferritin is the better stores marker — it reflects total body iron and falls early in depletion. Serum iron is highly variable hour-to-hour and is most useful as part of a panel (with TIBC and transferrin saturation) to characterize the type of iron disorder.
Primary source
Ferritin