From the Guidelines
To absorb iron supplements better, take them once a day, on an empty stomach, with 80 mg of ascorbic acid (vitamin C), and avoid consuming tea and coffee within an hour after taking iron. This approach is supported by a recent study published in Clinical Gastroenterology and Hepatology 1, which found that taking iron with vitamin C improves absorption by forming a chelate with iron and reducing ferric to ferrous iron. Additionally, a study from the same journal suggests that giving oral iron once a day at most is a reasonable approach, and every-other-day iron dosing may be better tolerated for some patients with similar or equal rates of iron absorption as daily dosing 1.
When choosing an oral iron formulation, ferrous iron salts (ferrous sulfate, ferrous fumarate, and ferrous gluconate) are a reasonable choice to start with because they are often the least expensive, although some patients may tolerate other products such as ferrous bisglycinate better 1. It is essential to note that side effects are common with oral iron, including constipation, diarrhea, and nausea, and taking iron more than once a day will not improve absorption but will increase side effects 1.
Key considerations to enhance iron absorption include:
- Taking iron on an empty stomach to minimize interference from other nutrients
- Avoiding tea and coffee within an hour after taking iron, as they are powerful inhibitors of iron absorption
- Considering every-other-day iron dosing if daily dosing is not well tolerated, as it may have similar or equal rates of iron absorption 1
- Choosing ferrous forms of iron, which are better absorbed than ferric forms
- Being mindful of the potential for interactions with other medications, such as antacids, and separating them from iron supplements by at least two hours.
From the Research
Iron Absorption
To absorb iron supplements better, consider the following:
- Take oral iron supplements on an empty stomach, as food can inhibit iron absorption 2
- Vitamin C can enhance iron absorption, so taking iron supplements with a glass of orange juice or other vitamin C-rich food may be helpful 2
- Avoid taking iron supplements with milk or dairy products, as calcium can inhibit iron absorption 2
- If you have a condition that impairs iron absorption, such as celiac disease or atrophic gastritis, you may need to take intravenous iron or a different form of iron supplement 2
Factors Affecting Iron Absorption
Several factors can affect iron absorption, including:
- The type of iron supplement taken (e.g. ferrous sulfate) 2
- The presence of other nutrients or substances that can inhibit or enhance iron absorption (e.g. vitamin C, calcium) 2
- Underlying medical conditions that can impair iron absorption (e.g. celiac disease, atrophic gastritis) 2
Note on Provided Studies
Only one of the provided studies, 2, is relevant to the topic of iron absorption and supplementation. The other studies, 3 and 4, appear to be unrelated to the topic and do not provide any useful information on iron absorption.