How quickly can a patient with iron deficiency anemia and Attention Deficit Hyperactivity Disorder (ADHD) feel the effects of oral iron therapy and what is the recommended dosing frequency?

Oral Iron Therapy: Timeline and Dosing Frequency

You should take 50-100 mg of elemental iron once daily in the morning on an empty stomach, and you can expect to feel symptom improvement within 2-4 weeks, with measurable hemoglobin increases detectable at 2 weeks. 1, 2

How Quickly You'll Feel Effects

Expect noticeable improvement in fatigue and other anemia symptoms within 2-4 weeks of starting treatment. 1, 2 The timeline breaks down as follows:

• At 2 weeks: Your hemoglobin should rise by at least 10 g/L (1 g/dL) if the treatment is working—failure to achieve this strongly predicts treatment failure with 90% sensitivity 3, 1, 2
• At 4 weeks: Most patients experience significant symptom relief and continued hemoglobin improvement 1, 2
• At 3 months after hemoglobin normalizes: Iron stores become adequately replenished, which is when treatment should be completed 3, 1, 2

For your ADHD symptoms specifically, if they're related to iron deficiency, improvement may take the full 3 months as iron stores replenish and dopaminergic function normalizes. 4

Optimal Dosing Frequency

Take iron once daily, not multiple times per day. 1, 2 Here's why this matters:

• Once-daily dosing (50-100 mg elemental iron) is the recommended approach because doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks subsequent iron absorption 2, 5
• Taking a second dose the same day results in 35-45% reduction in absorption from that second dose due to elevated hepcidin 2
• Take your dose in the morning on an empty stomach to maximize absorption 1, 2

If Standard Daily Dosing Causes Intolerable Side Effects

Consider alternate-day dosing with 100-200 mg elemental iron, which actually increases fractional iron absorption compared to daily dosing, though the rate of hemoglobin rise may be slower initially. 3, 2, 5 This approach:

• Allows hepcidin levels to subside by 48 hours, improving absorption of the next dose 5
• Reduces gastrointestinal side effects significantly 3, 6
• Was shown to be non-inferior to daily dosing in treating iron deficiency anemia 6

Practical Dosing Instructions

One ferrous sulfate 200 mg tablet (containing 65 mg elemental iron) taken once daily in the morning on an empty stomach is the most cost-effective regimen. 1, 2

• Take 1-2 hours before or after meals 2
• Avoid taking with tea, coffee, or calcium-containing foods which inhibit absorption 2
• Do not take multiple doses per day—this increases side effects without improving absorption 2

Monitoring Your Response

You should have your hemoglobin checked at 2 weeks to confirm the treatment is working. 3, 1 If your hemoglobin hasn't increased by at least 10 g/L at 2 weeks, this strongly predicts treatment failure and warrants investigation for:

• Non-compliance 3
• Continued blood loss 3
• Malabsorption 3
• Concurrent vitamin B12 or folate deficiency 3

Continue monitoring hemoglobin every 4 weeks until it normalizes, then continue treatment for an additional 3 months to replenish iron stores. 3, 1

Common Pitfalls to Avoid

• Don't take iron with food initially—while this reduces side effects, it also reduces absorption by up to 50% 1
• Don't switch between different ferrous salts (ferrous sulfate, ferrous fumarate, ferrous gluconate) expecting better tolerability—this is not supported by evidence 3, 2
• Don't use modified-release preparations—they are less suitable for prescribing according to guidelines 3, 2
• Don't rely on multivitamins alone—they contain insufficient elemental iron (typically ≤14 mg) for treating iron deficiency 2

When to Consider Alternatives

If you cannot tolerate oral iron despite these modifications, intravenous iron should be considered, as it produces a clinically meaningful hemoglobin response within one week. 3, 2