What is the appropriate management for a patient with a normal hemoglobin level, slightly elevated MCV, elevated ferritin, and low folate level?

Laboratory Interpretation and Management

This patient has normal hemoglobin with borderline low folate (6.8 ng/mL) and should receive oral folic acid supplementation 5 mg daily for at least 4 months, but only after confirming vitamin B12 levels are adequate to prevent masking B12 deficiency. 1, 2

Current Laboratory Analysis

Your labs show:

• Hemoglobin 13.73 g/dL: Normal (no anemia present) 3
• MCV 94.1 fL: Normal range (80-100 fL) 3
• Ferritin 179 ng/mL: Normal to mildly elevated 1
• Folate 6.8 ng/mL: Borderline low (deficiency defined as <10 nmol/L or <3.5 ng/mL depending on assay) 1, 4
• Iron 53 mcg/dL and TIBC 210 mcg/dL: Calculate transferrin saturation = 25%, which is normal 1

Critical Next Steps

Mandatory B12 Testing Before Folate Treatment

You must check vitamin B12 levels before starting any folate supplementation. 1, 2 This is the single most important pitfall to avoid:

• Giving folic acid doses >0.1 mg daily without excluding B12 deficiency can produce hematologic improvement while irreversible neurologic damage progresses 1, 2
• The FDA label explicitly states doses >0.4 mg should not be given until pernicious anemia is ruled out 2
• B12 deficiency is common (48.9% prevalence in some populations) and frequently coexists with folate deficiency 4, 5

Treatment Algorithm

If B12 is normal (>203 ng/L or >150 pmol/L): 1

• Start oral folic acid 5 mg daily for minimum 4 months 1, 2
• The usual therapeutic dose is up to 1 mg daily for adults, though resistant cases may require larger doses 2
• Doses >1 mg do not enhance hematologic effect and excess is excreted unchanged 2

If B12 is deficient (<150 pmol/L): 1

• Treat B12 deficiency FIRST with 1 mg vitamin B12 intramuscularly three times weekly for 2 weeks, then 1 mg every 2-3 months for life 1
• Only after initiating B12 treatment should you add folate supplementation 1

Why Folate Supplementation is Indicated

Despite your hemoglobin being normal, borderline low folate warrants treatment because:

• Folate levels <10 nmol/L indicate deficiency 1
• Your value of 6.8 ng/mL is in the borderline range where supplementation prevents progression to deficiency 4
• Coexisting nutritional deficiencies are common (12.5% folate deficiency, 48.9% B12 deficiency in young populations) 4
• Early treatment prevents development of megaloblastic anemia 5

Monitoring Response

• Recheck hemoglobin and folate levels after 4 months of treatment 2
• An increase in hemoglobin of ≥2 g/dL within 4 weeks indicates adequate response (though you're not anemic, this applies if anemia develops) 6
• Once corrected, maintenance folate is 0.4 mg daily for adults 2

Additional Considerations

Your mildly elevated ferritin (179 ng/mL) does not require intervention:

• This level is normal and does not indicate iron overload 7
• Ferritin can be mildly elevated with inflammation, but your level is not concerning 3
• No phlebotomy or iron restriction is needed 7