Ferrous Sulfate 325mg Dosing Directions
Take ferrous sulfate 325mg once daily in the morning on an empty stomach, as this optimizes absorption and minimizes gastrointestinal side effects compared to traditional multiple-daily-dose regimens. 1, 2
Standard Dosing Regimen
The FDA-approved directions specify taking 1 tablet two to three times daily for adults, without crushing or chewing the tablets. 2
However, recent evidence strongly supports once-daily dosing as superior to multiple daily doses, as doses ≥60mg elemental iron stimulate hepcidin elevation that persists for 24 hours and reduces absorption of subsequent doses. 1, 3
Each 325mg ferrous sulfate tablet contains approximately 65mg of elemental iron. 4, 2
Optimal Timing and Administration
Take the tablet in the morning (ideally around 8:00 AM) on an empty stomach for maximum absorption, as serum hepcidin increases throughout the day and reduces iron absorption when taken later. 1
If gastrointestinal side effects are intolerable, taking the tablet with meals is acceptable, though this reduces absorption somewhat. 1
Consider taking with 250-500mg vitamin C (or citrus juice) to enhance absorption, particularly if taking with food. 4, 1
Important Timing Restrictions
Avoid consuming tea or coffee within 1 hour of taking iron, as these are powerful inhibitors of iron absorption. 1
Separate iron from calcium supplements by 1-2 hours, as calcium interferes with iron absorption. 4
Do not take with antacids, milk, or fiber-containing foods, which reduce absorption. 1
Alternative Dosing for Side Effects
If severe gastrointestinal side effects occur despite once-daily dosing, consider every-other-day dosing (one tablet every 48 hours), which significantly increases fractional absorption and may improve tolerability. 1, 3
Alternate-day dosing resulted in 21.8% fractional iron absorption versus 16.3% with consecutive-day dosing in iron-depleted women, demonstrating superior efficacy. 3
Monitoring Response
Expect a hemoglobin rise of at least 10 g/L (1.0 g/dL) after 2-4 weeks of therapy; failure to achieve this strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%). 5, 6
Continue supplementation for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores. 5, 1
Common Pitfalls to Avoid
Do not take multiple doses per day thinking it will work faster—this actually decreases total absorption due to hepcidin elevation and increases side effects. 1, 3
Do not crush or chew tablets, as this may alter absorption and increase gastrointestinal irritation. 2
Do not discontinue prematurely due to black stools, which are a normal and expected effect of iron supplementation, not a side effect requiring cessation. 7
When to Consider Alternatives
Switch to intravenous iron if oral iron causes intolerable symptoms despite dosing adjustments, or if hemoglobin/iron stores fail to improve after 4-6 weeks despite adherence. 6, 1
Consider alternative oral formulations (ferrous fumarate 210mg or ferrous gluconate 300mg) if ferrous sulfate is not tolerated, though evidence for superior tolerability is limited. 4