Ferrous Sulfate For Anemia: Dosage, Side Effects, And More

Anemia is when your body can’t produce enough red blood cells, often due to a lack of iron. This can occur due to bleeding or an underlying issue.

Doctors can treat iron deficiency by supplementing with oral or intravenous iron; ferrous sulfate is one treatment option.

Let’s learn more about anemia and how ferrous sulfate can help. 

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What is iron deficiency anemia?

Iron is a key part of hemoglobin, the protein in red blood cells that transports oxygen through your body. Without sufficient iron, your body cannot produce healthy red blood cells, resulting in anemia. 

Causes of iron deficiency anemia can include: 

  • Gastrointestinal bleeding

  • Heavy menstrual periods

  • Childbirth

  • Traumatic injuries

  • Weight loss surgery 

  • Intestinal conditions that make it harder to absorb iron

How is iron deficiency anemia diagnosed?

Doctors commonly diagnose iron deficiency anemia through a complete blood count (CBC), a peripheral smear, and an iron profile. Your doctor will suspect iron deficiency anemia if you have symptoms of anemia, recently lost blood, or have a condition making it harder to absorb iron. 

Symptoms of anemia include:

  • Dizziness

  • Lightheadedness

  • Fatigue

  • Pica

  • Shortness of breath on exertion

Mild anemia often has no symptoms. Your doctor may only notice it when performing a CBC for routine physicals or when you are at risk of anemia, such as during pregnancy.

What is ferrous sulfate?

Ferrous sulfate (or sulphate) is an oral iron supplement available over the counter. It’s an iron salt your system can easily absorb, allowing you to get iron quickly. 

Ferrous iron salts like ferrous sulfate are the typical first-line therapy with better bioavailability and absorption than ferric iron salts.

Is ferrous sulfate good for anemia?

Ferrous sulfate is one of several iron salts that doctors use to treat anemia. They may pair it with folic acid and vitamin C to enhance absorption.

Currently, doctors recommend an alternate day single dose. Research has indicated that people may absorb iron better on this schedule.¹

Treatment with oral iron can take up to two months to remedy anemia and as long as six months to replenish iron stores. All oral iron supplements are about as effective.

Who can take ferrous sulfate?

Ferrous sulfate is typically recommended for adults, infants, and children. According to research, a lower dose of 3mg/kg elemental iron is suitable for young children.²

Who should avoid ferrous sulfate?

Ferrous sulfate is not suitable if you:

  • Have hemochromatosis, hemosiderosis, or any other condition causing excess iron levels

  • Have sickle cell anemia or thalassemia

  • Have stomach or bowel problems, including ulcers

  • Receive frequent blood transfusions

You should not take iron supplements within two hours of taking certain antibiotics, such as doxycycline, minocycline, or tetracycline. 

It’s best to avoid taking it within two hours of other medications. 

Furthermore, calcium, tea, coffee, and wine decrease iron absorption. 

It's also important not to overdose on iron, including medications that might contain iron.

Dosage of ferrous sulfate for iron deficiency anemia

The daily requirement for iron for people over 18 is 8–11mg for men and 8–18mg for non-pregnant women. Women need higher levels because of iron loss through menstruation. Most people can get their daily requirements from their diet.

The standard dosage for adults is 50–100 mg of elemental iron, which is typically one tablet three times daily. Each 325mg ferrous sulfate tablet contains approximately 65mg of elemental iron, of which your body absorbs about 25mg.³

This allows your body to replenish iron stores rapidly. You take ferrous sulfate until your body restores sufficient iron stores. Moderate anemia generally resolves within four weeks.

People with severe anemia will likely receive an IV iron infusion alongside oral supplementation.

You may lower your dosage if you have side effects, such as nausea and stomach discomfort. Some people may find a different iron salt suits their body better.

It’s crucial to keep iron supplements for adults away from young children.

Side effects of ferrous sulfate

Common side effects of ferrous sulfate include:

  • Constipation

  • Abdominal pain

  • Diarrhea

  • Nausea

  • Darkening of stools

You can relieve nausea and stomach pain by taking iron supplements with food or milk, although an empty stomach maximizes absorption. You can also lower your dosage, but you’ll have to take the supplements longer.

Other supplements for iron deficiency anemia

You can use other oral supplements for iron, including ferrous gluconate and ferrous fumarate. Some people may tolerate one of these more than others.

Your doctor may suggest IV iron supplementation if you: 

  • Have a condition that makes it hard to absorb iron, such as celiac disease

  • Have a chronic inflammatory bowel disease, which can reduce iron absorption

  • Cannot tolerate oral iron supplementation

  • Are pregnant

Dietary sources of iron

Generally, getting iron from your diet is best, although this can be challenging for people with some medical conditions. 

Foods that contain a lot of iron include:

  • Fortified breakfast cereals, which often contain 100% of your daily value

  • Oysters

  • White beans

  • Beef liver

  • Lentils

  • Spinach

  • Tofu

  • Dark chocolate

  • Kidney beans

  • Sardines

  • Chickpeas

  • Tomatoes

  • Beef

  • Potatoes

  • Cashew nuts

Your body absorbs heme iron, which comes from animal products, more readily than non-heme iron in plants and fortified cereals.

The lowdown

Iron deficiency anemia (IDA) is the most common anemia globally. You are more likely to have IDA if you menstruate, are pregnant, have recently had surgery or an injury, or have a condition that impacts iron absorption, among other issues.

Ferrous sulfate is a common short-term oral supplement to replenish iron stores when you’re anemic. The best way to prevent iron deficiency anemia is to eat iron-rich foods, but supplements can be helpful. Speak to your doctor if you’re concerned about anemia.

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