What is the recommended per enteral (by mouth) iron supplementation regimen for a patient with chronic kidney disease (CKD) and iron deficiency anemia?

Oral Iron Supplementation in CKD: Dosing and Administration

For adult CKD patients requiring oral iron supplementation, the recommended regimen is 200 mg of elemental iron daily, divided into 2-3 doses, taken on an empty stomach to maximize absorption. 1

Specific Dosing Recommendations

Elemental Iron Requirements

• Adult CKD patients should receive 200 mg of elemental iron per day, divided into 2-3 separate doses 1
• This translates to approximately 195 mg elemental iron daily when using standard formulations 2

Preferred Iron Formulations

The most cost-effective and reliable oral iron preparations are ionic iron salts 1:

• Ferrous sulfate 325 mg tablets = 65 mg elemental iron (requires ~3 tablets daily) 1
• Ferrous fumarate 325 mg tablets = 108 mg elemental iron (requires ~2 tablets daily) 1
• Ferrous gluconate 325 mg tablets = 35 mg elemental iron (requires ~6 tablets daily) 1

Iron polysaccharide preparations should be avoided as they are more expensive without being better tolerated or more effective than ionic iron salts 1

Critical Administration Guidelines

Timing for Optimal Absorption

• Iron must be taken on an empty stomach without food or other medications 1, 3
• Avoid food within 2 hours before or 1 hour after iron dosing, as food reduces absorption by up to 50% 1
• Separate aluminum-based phosphate binders from iron administration, as they significantly impair absorption 1

Managing Gastrointestinal Side Effects

If patients experience intolerance with standard twice-daily dosing 1:

• Start with lower doses and gradually increase
• Try smaller, more frequent doses throughout the day
• Switch to a different iron salt preparation
• Consider taking the supplement at bedtime

When Oral Iron Is Appropriate vs. When to Switch to IV

Initial Trial Period

• Oral iron is acceptable as a 1-3 month trial for non-dialysis CKD patients, though IV iron is the preferred first-line choice when feasible 1, 3
• Recheck TSAT and ferritin after the 1-3 month trial to assess response 1, 3

Indications to Switch to IV Iron

Most CKD patients cannot maintain adequate iron status with oral iron alone 1, and you should switch to IV iron when 1:

• Inadequate response after 1-3 months of oral therapy
• Inability to tolerate oral iron despite dose adjustments
• Patient is on hemodialysis (oral iron fails in most hemodialysis patients due to severely impaired intestinal absorption and greater ongoing iron losses) 4, 3

Iron Status Thresholds

• Initiate iron therapy when TSAT ≤30% AND ferritin ≤500 ng/mL 1, 5
• Stop iron supplementation when ferritin >500 ng/mL or TSAT >50%, as further hemoglobin increases are unlikely beyond these thresholds 1, 5

Monitoring Strategy

Frequency of Laboratory Assessment

• Check hemoglobin, TSAT, and ferritin every 3 months once treatment is established 1, 3
• Reassess iron parameters after completing the 1-3 month oral iron trial 1

Important Clinical Caveats

Hemodialysis Patients

There is no rationale for prescribing oral iron supplements to hemodialysis patients given their inconvenience, cost, side effects, and the fact that oral iron fails to maintain adequate iron stores in most hemodialysis patients 4. IV iron is strongly preferred for this population 3.

Comparative Efficacy

A randomized controlled trial demonstrated that IV iron (ferric carboxymaltose 1000 mg) achieved hemoglobin increases ≥1 g/dL in 60.4% of patients versus only 34.7% with oral ferrous sulfate 325 mg three times daily 2. Additionally, treatment-related adverse events were significantly fewer with IV iron (2.7%) compared to oral iron (26.2%) 2.

Safety Considerations

• Withhold IV iron during active infections, as iron is essential for microbial growth 3
• Avoid excessive iron administration by adhering to ferritin and TSAT upper limits 3, 5