Mildly Low Ferritin = Major Problem?

Feeling drained? Your patients might be, too, and the reason is often overlooked. A 2025 CMAJ article reports low iron is underdiagnosed & undertreated. Here’s why even “mildly low” ferritin matters and what the new Canadian guidelines mean for your patients.

Iron deficiency is a global health concern and disproportionately affects females due to

• menstruation,

• pregnancy, and

• socioeconomic factors.

  
  

Both nonanemic iron deficiency (NAID) and iron-deficiency anemia (IDA) are associated with significant morbidity - patients may show up on your clinic or in your SOO with concerns of fatigue, impaired cognition, and increased mortality, yet it is still not treated often enough.

Diagnosis of iron deficiency includes clinical history (particularly menstrual, dietary, and gastrointestinal), physical exam, and lab tests including complete blood count and ferritin.

What's a "normal" ferritin?

Canadian guidelines have raised the lower limit of normal ferritin values (to ≥30 µg/L for adults). This is relevant as there is emerging evidence that even mildly low ferritin has physiological consequences. Screening every 3 years in reproductive-aged females is reasonable, even though national guidelines remain inconsistent.

Find & Treat the Cause

Treatment is straightforward and includes addressing underlying causes (e.g. heavy menstrual bleeding), improving iron intake, and supplementing iron. Oral iron is first-line for most, taken once daily (or every other day if poorly GI tolerated), with slow but steady improvements in hemoglobin and ferritin over 3–6 months. Intravenous (IV) iron is reserved for those with severe anemia, malabsorption, or intolerance to oral iron.

EXAM TIP: P.I.E.

At The Review Course one of the exam tips we teach is P.I.E. The P stands for Pregnancy and in pregnancy, oral iron often fails to meet high physiological demands. IV iron may be needed in the second and third trimesters.

Screening ferritin early in pregnancy is crucial, as CBC alone may miss iron deficiency. Ultimately, prioritizing diagnosis and treatment of iron deficiency—especially in menstruating and pregnant patients—can address a critical, preventable contributor to global health inequity.

Source: CMAJ