The iron supplement ferrous sulfate is an iron salt with the chemical formula FeSO₄.

Iron salts are one type of the mineral iron. People often use them as a supplement to treat iron deficiency.

Ferrous sulfate is also called iron sulfate, green vitriol, and iron vitriol.

This article is an overview of ferrous sulfate, its benefits and side effects, and how you can use it to treat and prevent iron deficiency.

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What is ferrous sulfate?

Ferrous sulfate is just one of many forms of the metal element iron.

In its natural state, the solid mineral resembles small crystals. The crystals are typically a shade of yellow, brown, or bluish-green — hence why ferrous sulfate is sometimes called green vitriol (1).

Supplement makers use multiple types of iron in dietary supplements. Aside from ferrous sulfate, the most common are ferrous gluconate, ferric citrate, and ferric sulfate.

Most types of iron in supplements are in one of two forms — ferric or ferrous. This depends on the chemical state of the iron atoms.

The body absorbs ferrous forms of iron better than ferric forms. Thus, healthcare providers often consider ferrous forms, including ferrous sulfate, to be the best choice for iron supplements (2, 3, 4, 5).

Summary

Dietary iron supplements often use ferrous sulfate, a solid crystalline form of the mineral iron.

Benefits

The primary benefit of taking ferrous sulfate supplements is to maintain normal iron levels in the body.

Doing so may prevent you from experiencing iron deficiency, as well as the range of mild to severe side effects that often accompany it.

Here’s a closer look at the benefits of taking ferrous sulfate supplements.

Helps maintain normal blood iron levels

Iron is one of the most common elements on earth, and it’s an essential mineral. That means people need to consume it in their diet for optimal health.

The body primarily uses iron as part of the red blood cell proteins myoglobin and hemoglobin, which are essential for transporting and storing oxygen (6).

Iron also plays an important role in the formation of hormones, the health and development of the nervous system, and basic cell functioning (6).

Although many people consume iron as a dietary supplement, you can also find it naturally in many foods, including beans, spinach, potatoes, tomatoes, and particularly meat and seafood, including oysters, sardines, poultry, and beef (6).

Some foods, such as fortified breakfast cereals, are not naturally high in iron, but manufacturers add iron to make them a good source of this mineral (6).

Many of the highest sources of iron are animal products. Therefore, vegans, vegetarians, and people who do not consume many iron-rich foods as a part of their normal diet may benefit from taking ferrous sulfate iron supplements to help maintain their iron stores (7).

May prevent symptoms of iron deficiency

Taking ferrous sulfate supplements is a simple way to treat, prevent, or reverse low blood iron levels.

Preventing iron deficiency not only ensures that your body has enough of the essential nutrient to continue functioning properly but also can help you avoid many of the unpleasant side effects of low iron levels.

Some of the most notable side effects of low iron levels include (6, 8, 9, 10):

• fatigue
• headaches
• feeling weak
• low energy levels
• difficulty concentrating
• difficulty thinking clearly
• hair loss
• brittle nails
• upset stomach
• poor immunity
• heart palpitations
• restless leg syndrome
• shortness of breath
• the inability to regulate body temperature
• pica, an urge to eat nonfood items, such as paint or soap

This is a general overview — not a comprehensive list — of all the symptoms of low iron levels.

Symptoms may worsen as an iron deficiency progresses from mild to severe.

Used to treat iron deficiency anemia

Anemia is a condition that occurs when your blood has low amounts of red blood cells or hemoglobin (11).

Because iron is a critical part of the red blood cells responsible for transporting oxygen throughout the body, having iron deficiency is one of the most common causes of anemia (9, 12, 13).

Iron deficiency anemia (IDA) is a severe form of iron deficiency that has significant effects on the human body and may cause some of the more serious symptoms associated with iron deficiency.

One of the most common and effective treatments for IDA is taking an oral iron supplement, such as ferrous sulfate (14, 15).

Might improve surgical outcomes

Multiple research studies have cited having iron deficiency as a risk factor for increased rates of complications and mortality following surgery.

One study looked at the outcomes for 730 people who underwent heart surgery, including those with ferritin levels below 100 mcg per liter — a sign of iron deficiency (16).

The iron deficient participants were more likely to experience serious adverse events during surgery, including death. They also required a longer stay in the hospital, on average, after surgery (16).

Iron deficiency appears to have similar effects in other types of surgery. One study analyzed more than 227,000 surgical procedures and determined that even mild IDA prior to surgery increased the risk of health complications and mortality following the procedure (17).

Because ferrous sulfate supplements can treat and prevent iron deficiency, taking them prior to having surgery could improve the outcome and reduce the risk of complications (18).

However, it may take time to increase iron levels via supplementation.

Though oral iron supplements like ferrous sulfate are an effective way to increase iron stores in the body, a person may need to take supplements every day for 2–5 months to bring their iron stores up to normal levels (18, 19).

Thus, people with iron deficiency who do not have multiple months to try and increase iron stores prior to surgery may not benefit from ferrous sulfate supplements and require another type of iron therapy instead (20, 21).

Furthermore, research studies on iron therapy for people who have anemia before surgery are limited in size and scope. Scientists still need to conduct more high quality studies to investigate the best ways for people to increase their iron levels before surgery (21).

Summary

People primarily use ferrous sulfate supplements to prevent iron deficiencies, treat iron deficiency anemia, and maintain normal iron levels. The supplements may prevent the adverse side effects of iron deficiency.

Who’s at risk of low iron?

At certain stages of life, some groups of people have an increased need for iron. As such, they’re at a greater risk of low iron levels and iron deficiency. Others have lifestyles and diets that may lead to low iron levels.

People at the greatest risk of having low iron levels include (6, 15):

• infants
• children
• female adolescents
• pregnant people
• premenopausal people
• people with some chronic diseases
• people who donate blood often
• vegetarians and vegans

These groups may benefit most from ferrous sulfate supplements.

Summary

People in certain stages of life have increased iron needs and are more susceptible to iron deficiency. Children, female adolescents, pregnant people, and those with a chronic disease are some of the groups that may benefit most from ferrous sulfate.

How to take it

Ferrous sulfate supplements usually come in the form of oral tablets. You can also take them as a liquid drop.

The tablets are often red, green, or white.

The supplements may be listed under a variety of names, including:

• ferrous sulfate
• iron (Fe)
• Slow Fe
• Ironorm
• Feratab
• Ferosul
• Feosol
• Feospan
• Ferrograd
• Fer-In-Sol

If you want to take ferrous sulfate, it’s important to look closely at the label for the words “ferrous sulfate” rather than choosing any iron supplement.

This is because iron supplements can contain different types of iron.

Most supplements will clearly state the type of iron on the front label.

Many daily multivitamins also contain iron. However, there’s no guarantee that the iron they contain is ferrous sulfate unless it says so on the label.

Suggested dosage

In some cases, knowing the amount of ferrous sulfate to take can be tricky. Always talk to your healthcare provider to determine the right dosage for you.

There’s no official recommendation regarding the amount of ferrous sulfate you should take each day. The amount will vary depending on factors like your age, sex, health status, and the reason why you’re taking the supplements.

Many of the multivitamins containing iron provide around 18 mg or 100% of the Daily Value (DV) for iron. However, one ferrous sulfate tablet typically provides closer to 65 mg of iron, or 360% of the DV (6).

The general recommendation for treating iron deficiency or anemia is to take one to three 65-mg tablets daily.

That said, the total amount you should take each day may vary.

Some preliminary research suggests that taking iron supplements every other day — rather than daily — may be just as effective, if not more effective, than taking the supplements daily (22, 23).

Your healthcare provider will be able to provide a more specific and personalized recommendation regarding how much ferrous sulfate to take and how often, depending on your blood iron levels and personal circumstances.

When to take it

Certain foods and nutrients, such as calcium, zinc, or magnesium, might interfere with iron absorption and vice versa. Therefore, some people try to take ferrous sulfate supplements on an empty stomach for the greatest absorption (14, 24, 25).

However, taking ferrous sulfate supplements — or any other iron supplement — on an empty stomach may cause stomach pain and distress.

As such, healthcare providers generally recommended taking ferrous sulfate supplements with a meal.

Try taking ferrous sulfate supplements with meals that are low in calcium and do not include beverages that are high in phytates, such as coffee and tea (14, 26).

On the other hand, vitamin C may increase the amount of iron absorbed from ferrous sulfate supplements. Taking ferrous sulfate together with vitamin-C-rich juice or food might help your body absorb more iron (14, 27, 28).

Summary

There are many different forms of ferrous sulfate supplements on the market. Most are oral tablets, though liquid drops are also available. Always check with your healthcare provider before deciding how much ferrous sulfate to take.

Side effects

Side effects from ferrous sulfate supplements are fairly common (10).

The side effects people report most often are various types of gastrointestinal distress, including nausea, diarrhea, vomiting, abdominal pain, constipation, and dark or discolored stools (14, 29).

Some people have also reported experiencing heartburn after taking the supplements (29).

Furthermore, ferrous sulfate supplements may interact with certain medications.

Before starting ferrous sulfate supplements, be sure to let your healthcare provider know if you’re taking any of the following medications (6, 14):

• antacids, to treat indigestion
• proton pump inhibitors, to treat ulcers and gastroesophageal reflux disease (GERD)
• laxatives, to treat constipation
• levodopa, to treat Parkinson’s disease
• levothyroxine, to treat goiters, thyroid disease, and cancer

Summary

People taking ferrous sulfate commonly report side effects like nausea, heartburn, and abdominal pain. Furthermore, iron supplements may interact with certain medications, including antacids and proton pump inhibitors.

Can you take too much?

Ferrous sulfate is safe if you take it as a qualified healthcare provider has prescribed. However, this compound — and any other iron supplement — can be toxic in large amounts, especially in children (6, 30).

Some symptoms that may result from taking too much ferrous sulfate are coma, convulsions, organ failure, and even death (6).

Therefore, it’s extremely important to never take more ferrous sulfate than the amount your healthcare provider recommends.

Summary

Ferrous sulfate supplements may be toxic and even deadly in large amounts. Never take more than the dosage recommended by your healthcare provider, and always keep the supplements out of reach of children.

The bottom line

Ferrous sulfate is an iron salt that the body absorbs well. People commonly use it as an iron supplement to maintain normal blood iron levels or treat iron deficiency, including anemia.

Certain groups of people, including women, frequent blood donors, and people with a chronic disease, are at a greater risk of iron deficiency. They may benefit most from ferrous sulfate supplements.

The amount of ferrous sulfate you should take can vary significantly by individual.

Furthermore, the supplements are toxic in large amounts, and they may have side effects and interact with other medications.

For all these reasons, always check with your healthcare provider before taking ferrous sulfate or any iron supplement.