Slow Fe (Ferrous Sulfate Extended-Release) Supplementation Guidelines
Slow Fe, an extended-release ferrous sulfate formulation, should be taken as 1-2 tablets daily (50-100 mg elemental iron) on an empty stomach when possible, continued for 2-3 months after hemoglobin normalization to replenish iron stores, with hemoglobin monitoring every 4 weeks until normal range is achieved. 1
Optimal Administration
Take on an empty stomach for best absorption, though taking with food is acceptable if gastrointestinal side effects occur 1. The extended-release formulation (Slow Fe) demonstrates superior absorption compared to rapidly-disintegrating tablets, with 1.3-1.4 times higher iron absorption across all patient populations 2.
Critical Administration Rules:
- Never crush or chew tablets - this causes tooth staining, mouth irritation, and disrupts the extended-release mechanism 1
- Separate from antibiotics by at least 2 hours to avoid absorption interference 3
- Extended-release preparations show improved tolerability, which promotes better adherence 4
Standard Dosing Protocol
For iron deficiency anemia, administer 50-100 mg elemental iron daily 1. Slow Fe typically contains 50 mg elemental iron per tablet, making 1-2 tablets daily appropriate 5.
Dosing Considerations:
- Preparations with 28-50 mg elemental iron content minimize gastrointestinal side effects while maintaining efficacy 6
- Extended-release formulations allow for effective absorption with reduced side effects compared to higher-dose immediate-release products 4
- Excessive doses beyond 50-100 mg daily increase side effects without proportional benefit 6, 7
Monitoring Requirements
Check hemoglobin approximately every 4 weeks until normal range is achieved 1. An adequate response is defined as hemoglobin increase of at least 10 g/L (1 g/dL) after 2 weeks of daily therapy 1, 5.
Baseline Testing Should Include:
- Hemoglobin and hematocrit
- Mean cellular volume (MCV) and mean cellular hemoglobin (MCH)
- Serum ferritin (target >30 μg/L for adults >15 years)
- C-reactive protein to exclude false-negative ferritin results 6
Follow-up Protocol:
- Repeat basic blood tests at 8-10 weeks to assess treatment success 6
- If hemoglobin fails to increase by 1-2 g/dL in one month, consider non-compliance, malabsorption, continued bleeding, or alternative diagnosis 5
Treatment Duration
Continue oral iron for 2-3 months AFTER hemoglobin normalization to fully replenish iron stores 1, 4. This is a critical step - premature discontinuation before store repletion is a common pitfall 1.
Long-term Management:
- Patients with recurrent low ferritin benefit from intermittent oral supplementation 6
- Monitor iron stores every 6-12 months in high-risk patients 6
- Do NOT continue supplementation if ferritin is normal or elevated - this is potentially harmful 8, 6
When Oral Iron is Appropriate
Oral iron (including Slow Fe) should be first-line treatment for:
- Mild anemia in clinically inactive disease 9
- Patients without previous oral iron intolerance 9
- Hemoglobin >100 g/L 9
- Symptomatic iron deficiency without severe anemia 6
When to Switch to Intravenous Iron
Consider IV iron as first-line instead of oral preparations when:
- Clinically active inflammatory bowel disease 9
- Previous intolerance to oral iron 9
- Hemoglobin <100 g/L 9
- Malabsorption documented 5
- Urgent correction needed 6
- Chronic heart failure with iron deficiency 9
The European Society of Cardiology specifically recommends against oral iron in heart failure patients, as it has not been shown effective in this population 9.
Contraindications and Precautions
Absolute contraindications:
- Hemochromatosis or iron overload disorders 8
- Normal or elevated ferritin levels 8
- Active infection (iron promotes bacterial growth) 8
Common side effects include gastrointestinal discomfort, nausea, constipation, or diarrhea 3. These can be minimized by taking with meals, though this reduces absorption 1, 3.
Special Populations
High-Risk Groups Requiring Screening:
- Adolescents with heavy menstruation 6
- Pregnant women (universal supplementation recommended) 9
- Vegetarians/vegans 6
- High-performance athletes 6
- Patients with eating disorders or underweight 6
Pediatric Dosing:
For children 6-12 years, use ferritin cut-off of 15 μg/L; for adolescents 12-15 years, use 20 μg/L 6.
Safety Warning
Accidental iron overdose is a leading cause of fatal poisoning in children under 6 3. Keep all iron products out of reach of children and call poison control immediately if accidental overdose occurs 3.