When and How Is Ferrous Sulfate Used?

What is ferrous sulfate?

Ferrous sulfate is a form of iron that can be obtained through supplements. Our bodies mostly get iron through the different types of food we consume. Iron becomes a part of myoglobin and hemoglobin once it is inside the body. Myoglobin enables the storage of oxygen in muscle cells. Hemoglobin is the one that carries oxygen through the blood and to the body's different organs and tissues. 

Ferrous sulfate is commonly used for the treatment of iron deficiency anemia, which is a condition characterized by a reduced number of red blood cells (RBCs) or hemoglobin in the blood. This condition can occur due to poor diet, excessive bleeding, pregnancy, and other medical conditions. 

How is ferrous sulfate used?

Follow your doctor's instructions or use ferrous sulfate as directed on the product label. It is also very important not to take ferrous sulfate for a longer time than recommended and in larger amounts. 

Ferrous sulfate is usually available in the form of:

• Regular, coated, and extended-release tablets
• Regular and extended-release capsules
• Oral liquid in the form of drops, syrup, or elixir

Ferrous sulfate is usually taken between meals on an empty stomach three times a day. You can take it at least an hour before eating or two hours after a meal for maximum absorption. When ferrous sulfate is taken, the symptoms of iron deficiency tend to improve after a few days. However, in severe cases of iron deficiency, ferrous sulfate may be taken for up to six months. Taking vitamin C along with ferrous sulfate may also enhance absorption. 

Ferrous sulfate tablets must not be crushed or chewed. Its extended-release capsules should not be opened as well. Swallow the tablets and capsules whole. When taking ferrous sulfate drops, a special dropper is used to properly measure the dose. You can ask your pharmacist on how to dispense the liquid using the dropper. Ferrous sulfate drops may also be mixed with fruit juices or water. You may also directly place the drops in your mouth.

All ferrous sulfate products must be stored at room temperature and away from heat and moisture. 

Are there any side effects associated with ferrous sulfate use?

Yes. Ferrous sulfate may cause certain side effects. Its common side effects include:

• Dark stools
• Green-colored stools
• Diarrhea (loose stools)
• Constipation (hard stools)
• Abdominal pain
• Stomach cramps
• Nausea
• Vomiting
• Discoloration of urine
• Staining of teeth (oral solutions)
• Contact irritation
• Gastric irritation

Rare side effects of ferrous sulfate include:

• Gastrointestinal perforation (GP) or ruptured bowel
• Gastrointestinal obstruction or blocked intestine
• Gastrointestinal bleeding (GI bleed)

Seek immediate medical attention if you experience any of the following symptoms or side effects:

• Swelling of the face, mouth, throat, tongue, or lips
• Skin itching, rash, or hives
• Peeling skin
• Red, blistered, or swollen skin
• Difficulty breathing
• Wheezing
• Chest tightness
• Tightness in the throat
• Dysphagia (difficulty swallowing)
• Difficulty talking
• Abnormal changes in voice (voice hoarseness)
• Bloody, black, or tarry stools
• Fever
• Severe abdominal pain
• Persistent nausea and vomiting
• Vomiting blood that looks similar to coffee grounds

Warnings and Precautions 

Before taking ferrous sulfate, make sure to inform your doctor or pharmacist if you have an allergy to ferrous sulfate or any of its ingredients, including dyes such as tartrazine, which can be found in medications and processed foods. 

Your doctor must also have a list of all medications you are taking, including both nonprescription and prescription medications, supplements, vitamins, and herbal products. Make sure to inform your doctor if you are particularly taking any of the following medications:

• Tagamet (cimetidine)
• Larodopa, Sinemet (levodopa)
• Aldomet (methyldopa)
• Cuprimine (penicillamine)
• Chloramphenicol

If you are taking these medications, your doctor may change the dosages of your medications or carefully monitor you for any side effects. 

The following medications should also be taken two hours before or three hours after taking ferrous sulfate:

• Cipro (ciprofloxacin)
• Floxin (ofloxacin) 
• Zagam (sparfloxacin)
• Noroxin (norfloxacin)
• Levaquin (levofloxacin)
• Maxaquin (lomefloxacin)
• Penetrex (enoxacin)
• Cinobac (cinoxacin)
• NegGram (nalidixic acid)
• Demeclocycline
• Doxycycline
• Methacycline
• Minocycline
• Oxytetracycline
• Tetracycline

Antacids should not be taken at the same time with ferrous sulfate. Inform your doctor if you have or have had a history of colitis, ulcers, or intestinal disease. You should consult your doctor if you are pregnant, breastfeeding, or planning for pregnancy before taking ferrous sulfate. 

Mineral products and other multivitamins should not be taken two hours before or after taking ferrous sulfate. Taking these similar products along with ferrous sulfate may cause serious side effects or result in a mineral overdose. 

Keep ferrous sulfate away from children who are below 6 years old to avoid unintentional iron overdose. 

Make sure to inform your doctor or pharmacist if you are taking an iron supplement that contains folic acid, particularly if you have pernicious anemia or vitamin B12 deficiency. When folic acid is taken, certain blood tests to identify vitamin B12 deficiency may produce false results. When a vitamin B12 deficiency is left untreated, serious nerve problems may arise such as peripheral neuropathy. Symptoms of nerve problems include tingling, pain, and numbing sensations. Speak with your healthcare provider or pharmacist for more details. 

Ferrous sulfate in the form of chewable tablets may also contain the artificial sweetener called aspartame. People who have phenylketonuria (PKU) and other health conditions that restrict the consumption of phenylalanine or aspartame should consult their doctor before using this product. 

Those who have diabetes, liver disease, or alcohol dependence should also consult their doctor or pharmacist before using ferrous sulfate since oral solutions of this product may contain alcohol and/or sugar. 

Drug Interactions

Drug interactions may also occur when ferrous sulfate is taken along with certain medications. If you are taking other medications, make sure to discuss drug interactions with your doctor. 

Ferrous sulfate may seriously interact with any of the following medications:

• Ofloxacin
• Norfloxacin
• Gemifloxacin
• Fleroxacin
• Moxifloxacin
• Minocycline
• Tetracycline
• Oxytetracycline
• Demeclocycline
• Doxycycline
• Levofloxacin
• Lymecycline
• Mycophenolate
• Eltrombopag
• Dolutegravir

Moderate drug interactions are also reported with at least 30 different medications. 

The following are mild interactions of ferrous sulfate:

• Calcium chloride
• Calcium carbonate
• Calcium gluconate
• Calcium citrate
• Calcium acetate
• Carbidopa
• Acetohydroxamic acid
• Manganese
• Gymnema
• Didanosine

Special Dietary Instructions

Good dietary sources of iron include meat, fish, and animal liver, including fortified bread and cereals. You can add these iron-rich foods into your daily balanced diet.