Iron Supplement (Ferrous Sulfate)

Ferrous sulfate is an iron supplement you may use to treat iron-deficiency anemia. You may need ferrous sulfate if you don’t get enough iron through the foods you eat. Ferrous sulfate comes in tablet and liquid form. Side effects may include constipation, stomach cramps and other digestive issues. Only take an iron supplement as directed.

What is ferrous sulfate?

Ferrous sulfate is a type of iron supplement. You normally get all the iron you need from the foods you eat. Your healthcare provider may recommend ferrous sulfate if you don’t get enough iron in your diet. Iron supplements can be especially beneficial for women or people assigned female at birth.


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What is iron?

Iron is one of the minerals your body needs to function properly. Your body needs iron to produce hemoglobin and myoglobin. Hemoglobin is a protein in your red blood cells. Hemoglobin helps your blood carry oxygen from your lungs to all your body‘s tissues and organs. Myoglobin is a protein in your muscles and helps supply oxygen to the cells in your muscles.

If you don’t have enough iron, your body can’t make these proteins, and you may develop iron-deficiency anemia. Iron-deficiency anemia is the most common type of anemia. Anemia is a blood disorder in which your body doesn’t have enough red blood cells

What is iron-deficiency anemia?

Iron-deficiency anemia can occur if you don’t have enough iron in your body. The condition develops when you lack the iron that your red blood cells need. Factors that can lower your body's supply of iron include:

Blood loss

You lose iron when you lose blood. You can lose blood in many ways:

Issues with absorbing iron

Some health conditions and medications can decrease your body’s ability to absorb iron. These may include:

  • Rare genetic disorders that block your intestines from absorbing iron.
  • Endurance sports that cause athletes to lose iron through their gastrointestinal tracts.
  • Certain digestive conditions such as ulcerative colitis and Crohn’s disease.
  • Intestine and stomach surgeries, including weight loss surgery.
  • Conditions that can destroy too many red blood cells (certain infections, autoimmune diseases and inherited blood cell disorders).

Iron-deficiency anemia can also happen if your diet doesn't have enough iron in it or if you have an increase in your body's need for iron (for instance, during pregnancy).


What are the symptoms of iron-deficiency anemia?

You may not have any symptoms if you have a mild case of iron-deficiency anemia. Symptoms of more severe cases of the condition may include:

  • Feeling tired (fatigue).
  • Pale skin.
  • Difficulty breathing.
  • Chest pain.
  • Fast heartbeat.
  • Dizziness.
  • Headache.
  • Feeling cold (including the sensation that your hands or feet are colder than usual).
  • Infections (caused by problems with your immune system).
  • Craving for nonfood items such as ice or dirt.
  • Restless legs in which you have a strong urge to move your legs.

Who is most likely to develop iron-deficiency anemia?

Anyone can develop iron-deficiency anemia, although the following groups have a higher risk:

  • Menstruating and pregnant people.
  • Frequent blood donors.
  • People who have kidney failure (especially if they are on dialysis), because they have trouble making red blood cells.
  • Premature babies or infants with low birth weights.
  • People with certain cancers or heart failure.


How is anemia diagnosed?

Your healthcare provider may order a blood test to check your complete blood count. The blood test will measure your hemoglobin and how many red cells are in your body. If these levels are low, your provider can make a diagnosis of anemia.

How is anemia treated?

Depending on the cause of iron-deficiency anemia, your treatment will vary. Your healthcare provider may recommend eating foods that are high in iron. They may also suggest an oral (taken by mouth) iron supplement such as ferrous sulfate. If you can’t take an oral supplement, you may need to get iron through a vein (intravenously).

What foods are high in iron?

You can find iron naturally in many foods. Many food products have also been fortified with iron. Iron-rich foods include:

  • Lean meat and poultry.
  • Seafood such as salmon.
  • White beans, kidney beans, lentils and peas.
  • Nuts and dried fruits.
  • Green leafy vegetables such as spinach.
  • Fortified bread and breakfast cereals.

Your body can absorb iron from plant foods better when you eat it with meat, poultry, seafood and foods that are high in vitamin C. Foods that contain a lot of vitamin C include fruits and vegetables such as oranges, strawberries, tomatoes and broccoli.

What is oral iron supplementation?

In addition to eating foods that are rich in iron, you may have to take an oral iron supplement. The benefit of an oral iron supplement is it treats your symptoms by increasing the levels of iron and hemoglobin in your body.

The iron in your body is called "elemental iron." Oral iron supplements contain different amounts of elemental iron. When you choose a supplement, be sure to check the label to see how much elemental iron it contains. A greater amount of elemental iron means your body will absorb more iron.

What are the different types of ferrous sulfate?

There are many different types of oral iron supplements. Ferrous sulfate comes in tablet or liquid form:

  • Tablets: The most common tablet size is ferrous sulfate 325 milligrams (mg). Tablets come in standard or delayed (extended) release formats.
  • Liquid: You can also take ferrous sulfate as a liquid iron supplement. The liquid comes as an elixir or as drops.

How should I take iron supplements?

If your healthcare provider has recommended an iron supplement, use it only as directed. You should take the supplement on an empty stomach. Take your medication at least one hour before or two hours after you eat a meal.

If you’re using a tablet form, swallow the tablet whole. Don’t try to crush, chew or break it. If you’re using a liquid form, measure the medicine carefully. Use a dosing syringe, not a kitchen spoon. You may not get an accurate dose of the medication.

Your healthcare provider may recommend a special diet while you’re taking ferrous sulfate. Follow their instructions precisely. Store the supplement at room temperature, and keep it out of reach of children.

Other instructions to keep in mind:

  • Although the supplement works best on an empty stomach, you may want to take it with food so it doesn’t upset your stomach.
  • You shouldn't take iron supplements with milk, caffeine, antacids or calcium supplements.
  • Try to take your iron supplement with vitamin C (for example, a glass of orange juice) to increase absorption.

What are the side effects of ferrous sulfate?

Iron supplements can cause is constipation, so drink plenty of water. You may need to take a stool softener along with the supplement. Iron supplements can cause several other side effects. These may include:

The side effects of ferrous sulfate supplements are usually temporary. They should go away as your body gets used to the medication.

What are the best iron supplements?

Your healthcare provider will help you decide what the best iron supplement is best for you. They’ll also tell you how much iron you need to take every day. The best way to take the iron supplement is through two or more doses each day. This way your body absorbs the greatest amount of iron. However, you should take extended-release iron products once a day.

When will I start to feel better?

It may take one to four weeks (after you start your iron supplement) before you start to feel better. Continue to watch your symptoms and take note of side effects. If you have any questions or concerns, talk to your healthcare provider.

How long will I have to take an oral iron supplement?

Your healthcare provider will let you know how long you have to take an iron supplement. After your hemoglobin and iron levels are back to normal, you may need to continue the iron supplement for another six months. You may have intermittent blood tests to measure your iron level.

A note from Cleveland Clinic

Ferrous sulfate is a type of iron supplement that can help you prevent or treat iron-deficiency anemia. Check with your healthcare provider before you start on any supplements. If your provider recommended you start on ferrous sulfate, make sure to follow their guidance closely. Ferrous sulfate has many benefits but it can also cause side effects. Only take an iron supplement for as long as your provider instructed. Taking more iron than your body needs can cause serious health issues.

Medically Reviewed

Last reviewed on 05/24/2022.

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