10 Side Effects Of Iron Tablets You Must Know

side effects of iron tablets

If you have low levels of iron, your doctor may have advised you to take iron supplements as a quick fix. Usually, signs of iron deficiency show up only when the iron reserves in the liver, muscles, bone marrow, or spleen are exhausted and you may be on the verge of iron deficiency anemia. So though it’s possible to replenish your iron stores through iron-rich foods, recovery takes longer.

[pullquote] Daily iron requirment



  • Adult men: 8 mg
  • Women (19–50 years): 18 mg
  • Pregnant women: 27 mg
  • Babies (7–12 months): 11 mg [/pullquote]

Moreover, if you follow a vegetarian diet, it may take longer still since the non-heme iron obtained from plant sources is not absorbed as well as the heme iron from animal sources. And if you are a frequent drinker of tea or coffee, iron absorption may be further hindered.

It has been seen that blood counts become normal for most people after taking supplements for about 2 months. In about 6 to 12 months, it’s possible to shore up iron levels even in the bone marrow.1 2 However, the supplements come with a few side effects that you need to be aware of. They can occur as a response or reaction to the supplements themselves or as a result of overdose. We have listed the side effects in the order of severity.


1. Stained Teeth

Taking iron in a liquid form can result in stained teeth. Try mixing your supplement in fruit juice, tomato juice, or water and drink it in with a straw so that it doesn’t come in contact with your teeth. Brushing your teeth with peroxide or baking soda can help remove iron stains from your teeth.3

2. Black Stools

It’s normal for your stools to change color and become a grayish or greenish black color while you’re on iron tablets. In fact, some experts consider this to be a sign that your supplements are working. But black stools can also be a sign of internal bleeding. So check in with your doctor immediately if your stools look tarry and not just black or if they have streaks of blood. Also, speak to your doctor if your stomach feels sore or you get sharp pains in the abdomen.4


3. Constipation Or Diarrhea

Iron tablets can cause problems like abdominal pain, cramps, constipation, and diarrhea. Lowering the dose can help, or you may take the iron supplements with a little food (except dairy products or cereals), though this will reduce absorption. You can also increase your fiber and fluid intake or take a stool softener. Staying active also helps relieve constipation.5

4. Nausea And Vomiting

Higher doses of iron may cause vomiting or nausea. You may also experience a metallic taste in the mouth. However, these side effects can be controlled by reducing the dose. Your doctor will also be able to recommend another form of supplement that may suit you better. For instance, people who suffer severely from side effects when they take ferrous sulfate are prescribed a different supplement known as ferrous gluconate, which has a lower concentration of iron.


5. Reduced Absorption Of Zinc

Iron in large quantities can reduce the absorption of zinc. And zinc deficiency can have a range of effects like slowing down of growth in babies and children, the delaying of sexual development, and impotence. It can also manifest as hair loss, diarrhea, loss of appetite, and skin and eye sores. It might help if you take zinc-rich foods and iron tablets at different times. Your doctor may also recommend zinc supplements if you have a deficiency.6

6. Interaction With Some Medications

Iron tablets can reduce the absorption and effectiveness of certain medicines used to treat Parkinson’s disease, restless leg syndrome, goiter, hypothyroidism, and thyroid cancer. Leaving a gap of at least a couple of hours between these medications and iron supplements can be helpful.7


7. Risk Of Heart Attack

Excessive amounts of iron constrict the blood vessels and increase oxidation, thus raising the risk of atherosclerosis and consequently heart attacks and strokes. This results in high blood pressure and a rapid pulse. Significantly low blood pressure can also cause you to go into shock. Patients of kidney dialysis are often at risk of heart attacks because of the iron injections they receive to combat anemia.8

8. Fluid Build-Up In The Lungs

Taking large amounts of iron can cause fluids to accumulate in your lungs. And when fluids build up, you may experience symptoms like coughing up of blood, gurgling, grunting, or wheezing sounds when you breathe, shortness of breath, excessive sweating, and pale skin. Trouble breathing when you lie down and anxiety are also possible signs.9


9. Nervous System Disorders

Since the body cannot excrete the excess iron easily, an iron overdose can have a severe impact on your nervous system. You may experience a reduced level of consciousness as soon as half an hour to an hour after the overdose and may go into a coma. Other signs include drowsiness, dizziness, headache, fever, and a loss of interest in doing anything. Iron overdose may even result in seizures.

You need to get emergency medical attention if you notice signs of an iron overdose or suspect that someone has overdosed. Also, do keep in mind that symptoms can sometimes disappear after a few hours and then return after a day or later.


10. Poisoning

Iron can be extremely toxic if it’s taken in excessive amounts. The upper limit of iron per day has been defined as 40 mg till the age of 13 and 45 mg from the age of 14 onward. An overdose can be particularly dangerous for children and might happen if a child gets hold of adult multivitamin pills or prenatal vitamins. In fact, iron overdose is a leading reason for fatal poisoning in kids below the age of 6.10 Loss of color, flushing, and a bluish tinge in your fingertips and lips can be signs of an overdose.11

Avoid Iron Supplements If You Have These Conditions

If you have any of the following conditions, avoid iron supplements as they may increase your risk of iron toxicity.


Hemochromatosis is a genetically inherited disease that can cause iron to accumulate to toxic levels in the body. Without treatment, this disease can lead to problems like liver cancer, liver cirrhosis, and heart disease. People with this condition should not use iron supplements or vitamin C supplements, which increase iron absorption.

African Iron Overload

First observed among the people of African descent, this is a rare condition caused due to the high intake of dietary iron. The condition is believed to result from the consumption of a traditional African beer, which contains dissolved iron from metal drums in which it is brewed. People with this condition should avoid taking iron supplements.

The excess iron accumulates in the immune cells in the bone marrow and spleen and compromises the infection-fighting ability of the immune system. As the condition progresses, iron also accumulates in the liver cells, causing toxicity, liver disease, and even cancer.12

Use Iron Supplements Properly

Here are a few tips on how to use and store your iron tablets, so you can minimize side effects.

Keep Them In A Cool And Dry Place

Warmth and humidity can cause iron tablets to fall apart; so your bathroom cabinet might not be the ideal place to store them. Store your tablets in a cool, dry place that’s inaccessible to children.

Stick To The Prescription

Taking excessive amounts of iron can lead to significant medical problems. So check with your doctor and take pills as directed. Don’t take 2 doses or extra doses at the same time, even if you’re trying to make up for a missed dose.

Take It On An Empty Stomach

Iron is best absorbed on an empty stomach. However, as mentioned earlier, your doctor may recommend that you take it with a little food to ease side effects.

Avoid Taking It With Certain Foods

[pullquote]Avoid drinking tea or coffee with your iron supplement as they can hinder iron absorption.[/pullquote]

Calcium can interfere with the absorption of iron. So do not take calcium supplements or foods like milk along with your iron tablet. Also avoid having drinks or foods with caffeine and foods high in fiber like raw vegetables, bran, and whole grain along with iron – these too can make it tougher to absorb iron. Leave a gap of at least 2 hours between taking these foods and your iron supplement. You should also avoid taking antacids along with iron supplements.

Take It With Vitamin C

Vitamin C can help your body absorb iron. Therefore, some experts suggest drinking something rich in this vitamin, like orange juice, or taking a vitamin C supplement along with your iron tablet.13 14 Speak to your doctor about this before you try vitamin C supplements, though.

If you’ve been prescribed iron supplements, know that your dosage will change over time depending on the requirement of your body. So, it’s important that you visit your doctor once the course of your prescription is complete.