Can iron deficiency cause insomnia and extreme daytime fatigue?

Can Iron Deficiency Cause Insomnia and Extreme Daytime Fatigue?

Yes, iron deficiency with a ferritin of 12 μg/L can absolutely cause both insomnia and extreme daytime fatigue, even when serum iron appears normal at 216 μg/dL, because ferritin reflects iron stores while serum iron is a poor indicator of total body iron status. 1, 2

Understanding the Lab Values

Your patient's ferritin of 12 μg/L indicates depleted iron stores regardless of the serum iron level. 3, 1

• Ferritin <30 μg/L confirms iron deficiency in patients without active inflammation 1, 2
• Serum iron fluctuates throughout the day and after meals, making it an unreliable marker of iron status 2
• The combination of low ferritin with normal serum iron represents early-stage iron deficiency where stores are depleted but circulating iron hasn't yet dropped 3

Direct Link Between Iron Deficiency and Sleep/Fatigue Symptoms

Iron deficiency causes fatigue even without anemia, and treatment is strongly justified when symptoms are present. 1

Fatigue Mechanism

• Iron deficiency impairs oxygen delivery to tissues and affects cellular energy metabolism 2
• Subjective fatigue improves significantly with iron supplementation (standardized mean difference -0.38; 95% CI -0.52 to -0.23) in non-anemic iron-deficient adults 4
• Symptoms include fatigue, irritability, depression, difficulty concentrating, and exercise intolerance 2

Insomnia Mechanism

• Low iron stores are directly associated with restless legs syndrome (RLS) in 32-40% of iron-deficient patients 2
• RLS causes severe sleep onset insomnia with subjective sleep latency exceeding 60 minutes 5
• Iron deficiency with ferritin levels around 17 μg/L has been shown to cause chronic insomnia in teenagers, with sleep latency of 143 minutes improving to 23 minutes after iron supplementation 5
• Iron supplementation significantly improves sleep quality and RLS severity (p < 0.001) 6

Treatment Recommendations

Start with oral iron supplementation as first-line therapy for this patient. 2

Oral Iron Dosing

• Ferrous sulfate 325 mg daily or on alternate days is the standard approach 2
• Alternate-day dosing may improve absorption and reduce gastrointestinal side effects 3
• Provide 35-65 mg elemental iron daily initially; if inadequate response, increase to twice daily 3

When to Use Intravenous Iron

Switch to IV iron if: 1, 2

• Oral iron is not tolerated (constipation, nausea, diarrhea are common) 3
• No response after 1 month (hemoglobin rise <1.0 g/dL, ferritin remains low) 3
• Patient has malabsorption conditions (celiac disease, bariatric surgery, inflammatory bowel disease) 3, 2
• Active inflammatory conditions are present 3, 1

If IV iron is needed, give ferric carboxymaltose 1000 mg as a single dose over 15 minutes. 3, 1

Monitoring Response

Recheck labs after 8-10 weeks of oral supplementation (not earlier, as ferritin levels are falsely elevated immediately after IV iron). 3

Expected improvements: 3, 6, 5

• Hemoglobin should rise ≥1.0 g/dL
• Ferritin should normalize (target >30 μg/L, ideally >50 μg/L)
• Transferrin saturation should normalize
• Fatigue symptoms should improve within 4-12 weeks
• Sleep quality and RLS symptoms should improve significantly

Critical Pitfalls to Avoid

Do not dismiss symptoms based on normal serum iron alone - ferritin is the gold standard for assessing iron stores. 1, 2

Do not wait for anemia to develop before treating - iron deficiency causes symptoms and impairs quality of life even without anemia, and treatment is strongly justified when symptoms are present. 1

Evaluate for underlying causes of iron deficiency, including: 2

• Gastrointestinal bleeding (most common in adults)
• Heavy menstrual bleeding (if applicable)
• Malabsorption disorders
• Dietary insufficiency
• Chronic inflammatory conditions