Updated: May 3
The first time I was told my iron levels were too low, I diligently started taking an iron supplement in the morning with my breakfast. Months later, my iron levels had barely changed. Unfortunately, increasing your iron levels is much more complex than popping a multi-vitamin first thing in the morning. So, if you've been told your iron levels are low and your doctor is recommending increasing your iron intake, there are a few things you need to know about first.
A Little Background Information About Iron
Iron is a component of our blood which carries oxygen from our lungs to other tissues in the body. It supports muscle metabolism, neurological development, and helps create some hormones (1).
Most commonly, when we talk about iron deficiencies, we hear about it causing fatigue. But it can also cause gastrointestinal issues, muscle weakness, difficulty concentrating, poor cognitive function, poor immune function, and more (2).
Whether you're planning to increase your iron intake through food or through a supplement, you should know that there are two types of iron: heme and non-heme. Heme iron is found in animal-based foods including red meat, seafood, and poultry. Non-heme iron is found in plant-based and fortified foods, but can also be found in animal products (3). Heme iron is more bioavailable, meaning it is absorbed more easily than non-heme iron. For this reason, folks who follow a vegetarian or vegan diet need to be consuming higher amounts of iron-rich foods.
Maximizing Iron Absorption
You might already know that vitamin C has been found to help increase iron absorption. But, if you're looking to maximize your absorption, consider taking a vitamin C tablet with your iron, rather than consuming foods with high levels of vitamin C. Fruits and vegetables are full of all kinds of health-promoting benefits such as vitamins, minerals, fibre, and something called polyphenols. Polyphenols are packed with antioxidants that help reduce the effects of free radicals. But, they also hinder iron absorption (4). And, in case you're wondering the same thing I did, it seems that fruit or vegetable juice still contains polyphenols, too (5).
Avoid drinking coffee and tea at the same time you consume iron-rich foods or supplements. Polyphenols are also present in coffee and tea (including green and Oolong teas!) (6), so for this reason, it's best to enjoy them at least an hour before or after consuming iron-rich foods or supplements.
Along with polyphenols, calcium hinders iron absorption, too. In addition to dairy, other foods that are great sources of calcium include salmon, kale and collard greens, tofu, broccoli, and almonds. Another source of calcium we tend to forget about are antacids such as TUMS. When possible, avoid consuming high calcium foods or supplements when also consuming iron (7).
Whole grains and legumes can also limit iron absorption. Whole grains and legumes contain a compound known as phytates, or phytic acid. Phytic acid limits absorption of different minerals, including iron, by up to 50% (8). Soaking or sprouting whole grains, seeds, and legumes can reduce phytate content substantially, so if you must take your iron with whole grains or legumes, get familiar with the process of soaking them ahead of time (or look for food products with grains that have already been sprouted).
Supplementing with Iron
As a nutrition coach (and not a doctor), I will never tell you specifically to take an iron supplement (or any supplement). However, if your doctor has advised that you begin oral supplementation, these 3 tips can help ensure you get the most out of your supplements.
Do not take iron supplements with other medications. In some cases, iron can decrease the effectiveness of medications. In other cases, certain medications can interfere with the absorption of iron (9). I encourage all my clients taking prescription medications to speak with their pharmacist prior to starting supplementation of any kind, but if that's not available to you, it's best to take iron supplements on their own.
Taking iron supplements on alternate days may reduce gastrointestinal side effects. Supplemental iron is known for being hard on the stomach and can cause symptoms such as nausea and constipation. Studies have shown that supplementing iron every other day may actually improve iron absorption, while being easier on the stomach (10).
Not all iron supplements are the same. The type of iron found in your supplements can make a big difference on absorption, and also on gastrointestinal side effects. For better absorption, look for ferrous iron over ferric iron (11). If you find iron is hard on your stomach, consider trying supplements made with heme iron polypeptides or polysaccharide iron complexes (12), as they may be gentler on the stomach. As an extra bonus, research also indicates that ascorbic acid (vitamin C) is not needed for absorption of either the polypeptide or polysaccharide formulations (13).
Replenishing iron levels takes time, and supplements can get expensive. If you're planning on taking an iron supplement, you may find it easier/most effective to take it on an empty stomach (if it doesn't cause you an upset stomach), rather than trying to keep all of this information straight.
I hope that this guide helps you maximize the effectiveness of your increase in iron (be it through foods or supplementation). Remember, this information is meant to compliment, not replace, any recommendations made by your primary health care provider. Always listen and follow their advice and speak with a pharmacist prior to beginning or changing any supplements.
Cheering You On, Jenna xo
(1-3, 7, 9, 11-12) National Institutes of Health Office of Dietary Supplements (2022, April 5). Iron.
Retrieved April 25, 2023, from https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
(4) Ems T, St Lucia K, Huecker MR. Biochemistry, Iron Absorption. [Updated 2022 Apr 21]. In: StatPearls
[Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:
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(6) Fukushima, Y. et al., (2009, February 2). Coffee and Green Tea As a Large Source of Antioxidant
Polyphenols in the Japanese Population. Journal of Agricultural and Food Chemistry. Retrieved
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(8) Hurrell R. F. (2004). Phytic acid degradation as a means of improving iron absorption. International
journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und
Ernahrungsforschung. Journal international de vitaminologie et de nutrition, 74(6), 445–452.
(10) Stoffel, N. U., Zeder, C., Brittenham, G. M., Moretti, D., & Zimmermann, M. B. (2020). Iron absorption
from supplements is greater with alternate day than with consecutive day dosing in iron-deficient
anemic women. Haematologica,105(5),1232–1239. https://doi.org/10.3324/haematol.2019.220830
(13) Ning, S., & Zeller, M. (2019, December 6). Management of iron deficiency. Retrieved April 25, 2023,