Last updated: August 27, 2021

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We're sure you've heard of anemia at some point in your life. If you're a woman, you've probably even had the symptoms of anemia at one point. The fatigue and experienced weakness triggered by anemia are in most cases due to a decrease in the iron reserves in your blood.

Health and nutrition experts very often recommend iron supplements to treat anemia. Outside the medical field, few people know about the secrets of this nutritional supplement. In the following article we attempt to explain everything you need to know about iron supplements and how to make the most of this useful mineral.


  • Iron is a mineral necessary for the synthesis of hemoglobin from red blood cells. It allows the transport of nutrients and oxygen in the body and acts as a catalyst for important chemical reactions.
  • The recommended dosage of this supplement and the stipulated treatment time should not be exceeded. Otherwise, iron can cause an oxidation of tissues that could cause damage to your body.
  • When deciding on an iron supplement, one must take into account the allergens it may contain, its form (solid or liquid) and the presence of dyes that can stain your teeth. If you are  a vegan or vegetarian, you can choose from a variety of iron supplements tailored for your needs.

The Best Iron Supplements: Our Picks

Shopping Guide: Everything you should know about iron supplements

Iron supplements were first used in 1832 by the French doctor Pierre Blaud. Since then, iron supplements have been used as a first-line treatment for the most common nutritional deficiency in the world, known as anemia or iron deficiency.

It is recommended to take the iron supplement on an empty stomach.
(Source: Petro: 42125023/

What is iron?

Iron is a very abundant metal in the earth. It makes up approximately 5% of the earth's crust. However, in the field of nutrition, this substance is indispensable in small quantities for the proper functioning of the human body. Your body's cells strictly regulate its absorption and metabolism.

Iron is involved in many processes of human biology. This mineral allows certain chemical reactions to take place and forms an essential part of two proteins responsible for the transport of oxygen and nutrients (myoglobin and haemoglobin). These functions are explained in detail below:

  • Enzymatic functions (chemical reactants): Iron plays an important role in the synthesis of DNA, the formation of collagen, the regulation of the immune system, the defence of the organism against disease-causing bacteria and the regulation of blood pH, among others.
  • Myoglobin formation: Myoglobin is a protein that stores oxygen in skeletal muscle (which deals with voluntary movements) and in the myocardium (heart muscle). Thanks to iron, this protein can form correctly and release oxygen to the muscle fibers whenever necessary.
  • Hemoglobin formation: Hemoglobin has a structure similar to myoglobin. This protein is found in red blood cells, giving them the capacity to transport oxygen to the tissues that need it and to remove the carbon dioxide resulting from cellular metabolism. Iron is needed for the formation of this compound.

Iron can be found in animal foods and green vegetables. (Source: Tatjana Baibakova: 55560042/

A healthy adult will have iron reserves ranging from 1-3 grams. However, cellular metabolism will degrade part of the iron stored in the body on a daily basis. If you are a woman in the childbearing age, these losses will be even greater. The recommended daily amount (RDA) of iron to replenish these reserves can be found in the table below:

Population group Milligrams/day (mg/day)
Infants up to 6 months 0.3 mg/day
Infants up to 12 months 11 mg/day
Boys and girls between 1-5 years 7 mg/day
Boys and girls between 6-11 years 10 mg/day
Male adolescents (12-18 years) 11 mg/day
Female adolescents (12-18 years) 15 mg/day
Adult males (18-99 years) 8 mg/day
Adult females (of childbearing age) 18 mg/day
Pregnant women 27 mg/day
Breastfeeding women 9 mg/day
Postmenopausal or non-menstruating women 8 mg/day


What are the symptoms of iron deficiency?

Iron deficiency will negatively impact all processes that depend on this mineral, especially influencing negatively the formation of hemoglobin. When this blood protein decreases through synthesis, the number of red blood cells decrease accordingly. This pathology is known as iron-deficiency anemia. Its signs and symptoms are summarised in the following list:

Mild iron deficiency anemia

  • Fatigue: Fatigue from activities that previously did not involve any effort is usually one of the first symptoms of anemia. As the amount of hemoglobin decreases, body tissues (including muscle and brain) receive less blood and are more susceptible to exhaustion.
  • Pallor: Hemoglobin gives blood its characteristic crimson colour. A deficit of iron (and therefore of hemoglobin) will cause the skin to turn pale. In dark-skinned people, this pallor can be seen in the mucous membranes (for example, in the inner lining of the eyelids, which will appear whitish instead of pinkish).
  • Headache: If the transport of oxygen and nutrients to the brain is compromised by a lack of iron, recurrent headaches may develop.
  • Lack of concentration: Decreased cerebral oxygenation can make it difficult to concentrate at work and school.
  • Fragile nails and hair: The lack of blood supply to hair and nails will return to these fragile tissues. The hair will lose luster and may fall out if the lack of iron is severe enough. In the case of nails, they will tend to break easily and may take on a concave appearance known as coilonychia.
  • Strange cravings: A lack of iron can cause a strange desire to eat ice, clay, earth, chalk, or lime on walls. This is the body's way of trying to recover some of the mineral in which it is deficient.
  • Anxiety: Lack of tissue oxygen caused by iron deficiency can lead to a state of constant nervousness and anxiety.
  • More frequent infections: Iron is essential for the proper functioning of the immune system. Its deficit will affect the function of the white blood cells and make it difficult to destroy bacteria, which will lead to more infections such as colds and gastroenteritis.

Severe iron-deficiency anemia

  • Lack of appetite: It has been seen that in some people, anemia can cause a state of weakness and loss of appetite that results in a loss of the desire to eat. Decreased intake will further worsen the anemia, creating a vicious cycle.
  • Palpitations and fast heart rate: Your heart muscle will try to compensate for the decreased hemoglobin content by increasing the frequency of your heartbeat. This will increase the speed at which blood reaches different body parts, but will cause tachycardia and palpitations.
  • Restless legs syndrome: The syndrome has been linked to iron deficiency with a high correlation. Due to this syndrome, there is an unpleasant tingling in the legs that usually appears during rest periods of our body and can cause insomnia to those who suffer from it.
  • In children and adolescents, reduced growth: Iron is essential for the proper development of younger people. If anemia is not treated in time, it could harm the growth of young children.
  • Low-weight babies: It has been shown that pregnant women with very severe anemia give birth to children with a lower weight and higher rates of complications. Mild anemia, on the other hand, is not a cause for concern and is not considered harmful to babies of pregnant women.

Lack of iron in the body can cause fatigue, and tiredness. You can treat anemnia (Fuente: Olena Kachmar: 76170550/

There are several different causes of iron deficiency. Poor iron intake, poor absorption, increased loss of iron or increased nutritional requirements can lead to iron deficiency anemia. The groups or populations at increased risk for this deficiency are listed below:

Decreased iron intake

  • Individuals who follow diets rich in carbohydrates and poor in animal products (especially vegans and vegetarians)
  • People who undergo hypocaloric slimming diets
  • People with eating disorders

Poor iron absorption

  • People affected by celiac disease
  • People Affected by Crohn's Disease
  • People affected by ulcerative colitis
  • Individuals who have undergone interventions in which part of the intestine or stomach is removed (bariatric surgery or surgeries for the treatment of tumors, Crohn's disease, or colitis)

Increased loss of iron

  • Women with heavy or endometriosis-affected periods
  • People who lose blood due to any pathology (esophageal varicose veins or colon cancer, mainly)

Increased nutritional requirements

  • Pregnant women
  • Breastfeeding women
  • Growing Children and Adolescents
  • People who practice very demanding sports
  • Stressed people (students in exam season, workers with demanding jobs)

In most cases, people with iron deficiency anemia are women of childbearing age because large amounts of iron are lost during menstruation. Anemias that occur in people who do not menstruate may have a more serious cause and should be thoroughly investigated by a physician.

The absence of iron can make your nails weak and break more easily. (Source: Subbotina: 79663441/

What foods are rich in iron?

Iron can be obtained from foods of animal origin (especially pork, veal and chicken viscera, legumes (especially lentils) and some green leafy vegetables (such as spinach). More detailed information on the main iron-rich foods can be found in the table below:

Food (100 grams) Amount of iron (milligrams) Type of iron Percent of recommended daily allowance (for a woman of childbearing age)
Clams 28 Heme 155%
Lentils 6.6 No heme 37%
Veal viscera (liver) 6.5 Heme 36%
Pumpkin seeds 4.2 No heme 23%
Spinach 3.6 No heme 20%
Tofu 3.5 Heme 19%
Dark chocolate 3.3 No heme 18%
Canned sardines 3 Heme 17%
Quinoa 2.8 No heme 15%
Red meat (pork or veal) 2.7 Heme 15%
Turkey 2.3 Heme 13%
Broccoli 1 No heme 6%


With so many iron-rich plant-based foods, it may seem odd that vegans and vegetarians are among the population groups most at risk of iron deficiency. However, there is an important difference between the iron found in foods of animal origin (heme) and that of vegetable origin (non-heme).

Heme iron is available in animal haemoglobin molecules. Its structure makes it easier for the human organism to absorb and incorporate it into cells. On the contrary, the assimilation of non-heme iron is more complicated and not all the ingested content ends up passing into the bloodstream.

Dark chocolate is one of the foods of vegetable origin that is rich in iron. (Source: Liliya Kandrashevich: 35649126/

In addition, foods of plant origin contain other products (e.g. phytates) that inhibit the body's absorption of iron. Vegans and vegetarians will have to incorporate plenty of iron-rich foods and combine them with substances that increase their absorption, such as vitamin C.

Who can benefit from an iron supplement?

If symptoms of anemia appear, it is advisable to see a health professional to rule out potentially serious problems such as colon cancer. If it is revealed that the deficit of this mineral is due to an unbalanced diet or an increase in losses due to physiological causes, an iron supplement will be a useful addition to your diet.

Fortunately the most benign type of anemia (iron deficiency) can usually be detected with a simple blood test, which is especially important for young people, women with heavy periods, and vegans. These groups will benefit greatly from the use of an iron supplement, noting the following effects after treatment:

  • Fatigue relief
  • Better exercise tolerance
  • Improved condition of hair and nails
  • Relief of restless legs syndrome
  • Relief of palpitations
  • Improved concentration
  • Anxiety relief

Quinoa is rich in iron. Make sure ti complement it in your diet.
(Source: Svetlana Kolpakova: 29868452/

What types of iron supplements are there?

When buying a new iron supplement, we will find different presentations of this mineral. The truth is that the iron molecule is very unstable on its own, being necessary to combine it with other substances so that it does not degrade and lose its functions. In the following list you can find more information about these preparations:

  • Ferrous sulphate: This is the most popular iron preparation and is part of most iron supplements. Although it is an affordable and safe product, it should be taken on an empty stomach so as not to affect its absorption. It can cause unpleasant gastrointestinal effects.
  • Ferrous Gluconate: This type of supplement contains two molecules of amino acids that increase its absorption, so it can be taken along with food. In addition, this substance produces less gastrointestinal discomfort compared to ferrous sulfate.
  • Ferrous Bisglycinate: This supplement is softer on the digestive system of more sensitive people. Generally, fewer side effects will occur during the use of bisglycinate.
  • Other preparations (lactate and citrate): There are numerous combinations between iron and other substances (such as lactate or citrate). In almost all cases, it is recommended to opt for supplements offering iron in ferrous form (Fe II) rather than ferric iron (Fe III). The ferrous form of this mineral is more easily absorbed.

In addition, we will find combinations of iron with other nutrients, such as Vitamin C (an antioxidant capable of improving the absorption of this mineral), folic acid (another nutrient essential for the synthesis of red blood cells) and Vitamin B12 (a compound that tends to be lacking in vegan diets).

How should you intake iron supplements?

First of all, we recommend that you choose a supplement that provides 100% of the recommended daily amount (RDA) for an individual of your characteristics. Most items are used to make up for the iron deficiency of women with heavy periods and usually offer doses of 18 mg. If you are a man, this amount will be excessive.

It is recommended to take these supplements on an empty stomach (or at least two to three hours before or after meals). It is essential to take your iron at least two hours before or after taking coffee, tea, eggs, dairy products, calcium supplements or certain medicines, as these substances inhibit the absorption of this mineral (especially ferrous sulphate).

However, taking your iron supplement with a piece of fruit (preferably a citrus fruit) or with a glass of juice will favour the absorption of this mineral. The vitamin C in these foods helps the iron pass into its ferrous form, improving the incorporation of the nutrient into the cells of the body.

It is important to eat a balanced diet.
(Source: Mark Bowden: 31050321/

As the goal of iron treatment is to raise the hemoglobin count to normal parameters (13-17 grams per deciliter in men and 12-15 grams per deciliter in women) and replenish body iron stores, it is recommended to use the supplement for two months in a row. Afterwards, a new medical examination should be requested.

What precautions should I take during iron supplementation?

Iron supplementation is generally considered very safe. In healthy people who do not take other medication, iron supplements will not produce great adverse effects if used according to the instructions for use. However, the minor discomfort that may occur during taking it should be taken into account:

  • Gastrointestinal discomfort: Iron can cause abdominal pain in some people. These pains can range from mild to severe. In these cases it is advisable to take the supplement at night (so that the discomfort is less perceived during sleep) or eat a small amount of food (such as bread or biscuits) with the iron supplement.
  • Constipation or diarrhoea: Depending on the individual characteristics of each person and the brand of iron supplement used, diarrhea or constipation may occur. Many times it will be necessary to change your diet (for example, providing more fiber in the case of constipation) or choose another supplement that your body is better able to absorb.
  • Dark stools: Iron supplements can give a characteristic deep black colour to stools. This effect is completely harmless. However, dark stools in a person who does not take iron are a sign of disease and may cause panic among people who are not aware of this side effect.

Iron supplements can be harmful if used at higher doses than recommended for long periods of time. This molecule has been shown to have an oxidising capacity that can impair the health of body tissues. For this reason, it is recommended to use iron only when necessary and for the shortest time possible.

On the other hand, iron supplements have numerous pharmacological interactions with substances widely used in the treatment of common diseases. It will be necessary to consult with a healthcare professional before starting treatment with iron supplements if any of the following preparations are also used:

  • Antiparkinsonian medication: Levodopa
  • Thyroid medication: Levothyroxine
  • Antacids: Omeprazole and similar
  • Antibiotics: Quinolones, penicillamine, penicillin
  • Supplements: Calcium and zinc

People with conditions that affect iron metabolism (for example, hemochromatosis) should not take these supplements without medical supervision. In the case of pregnant women and those under the age of eighteen, iron has been shown to be safe as long as the treatment is supervised and personalised by a professional.

Elaine K. LuoMD and specialist in food sciences
"Foods from plant sources only provide non-heme iron. Non-heme sources usually account for more of a person's daily intake than heme iron, but the body does not absorb it as well as heme iron.".

Shopping Criteria

If you want to get the most out of your iron supplement, you'll need to choose a preparation that suits your individual needs. The following purchase criteria will help you when deciding on one item or another and will allow you to make an effective and economical iron supplement:

Allergens and intolerances

Allergic reactions to iron supplements have been described. Ferrous sulfate is capable of generating itchy skin (pruritus), beans (hives), and redness of the skin. In exceptional cases, this compound may lead to an anaphylactic reaction (swelling of the lips, tongue or throat). If such a reaction occurs, it is essential to seek medical help.

Remember that iron is often combined with other substances to give the supplement molecular stability. If you are allergic to gluten, soya, seafood, lactose or any other product, don't forget to check the label of your supplement to rule out the presence of any allergen.

Iron-containing foods such as broccoli improve concentration.
(Source: Brent Hofacker: 36930759/

Combination with other nutrients

Although it may be very attractive to take several vitamins and minerals in one capsule, the combinations of iron, vitamin B12 and folic acid have a high price and a very specific audience. Vegans and pregnant women will benefit from these preparations, while others can save a few dollars by choosing simpler supplements.

In the case of ascorbic acid or vitamin C, this substance has been shown to increase the absorption of iron in the duodenum. However, it is possible to achieve a similar increase in the bioavailability of this compound by taking your iron supplement with a glass of orange juice or a piece of fruit.


Iron supplements are usually given in capsule or tablet form. However, if you find this format particularly uncomfortable (as is the case for people with difficulty swallowing solid foods) you can get iron in drinkable form. This format is just as effective as solid supplements, although somewhat more expensive.

By definition, anemia is a syndrome characterized by a reduction in hemoglobin concentration, a decrease in the number of red blood cells, or an alteration in their size. Iron deficiency anemia is the most common, but there are other types, such as vitamin B12 deficiency anemia.


Iron, left for a long time in the mouth, has the ability to stain teeth of a tone similar to "oxidised iron". If you use this supplement in tablets, do not let the tablet melt in your mouth. In the case of drinkable iron, it is advisable to take it with a "straw" to avoid contact with teeth.

Vegan and vegetarian nutrition

Iron is a nutrient that may be lacking in the diet of vegans and vegetarians. Therefore, it won't be difficult for you to find supplements that respect the dietary restrictions of plant-based diets. Numerous brands manufacture preparations specially designed for vegans and vegetarians. These supplements may also contain vitamin B12.


Iron deficiency affects millions of people worldwide. Women of childbearing age, vegans and young athletes can suffer the unpleasant consequences of anemia, if they fail to balance the metabolism of this mineral through a proper diet. An iron supplement can be a great help to these people.

Iron supplements will restore your energy in a matter of weeks, although you will have to use them for a few more months to replenish your body's iron reserves. Remember to use them only for as long as you need them and in the right dosage; or you'll run the risk of ending up "rusty"!

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(Featured image source: Andriiakhina: 49483789/