The signs that iron pills are working vary but some people may notice an improvement in energy and other anemia symptoms. However, a person without noticeable anemia symptoms may see little change.

People often begin responding to iron pills within 2 weeks. A doctor can monitor if supplementation is working by performing a blood test.

Keep reading to learn more about the signs that iron pills are working, as well as how long they take to work, and signs they may not be working.

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Iron pills can help treat iron deficiency anemia. Whether or not these supplements cause noticeable improvements in symptoms will depend on how anemia affects a person before they begin taking them.

Most people with iron deficiency have no symptoms, so taking iron pills may not result in any obvious changes to how they feel. A doctor can verify if the pills are working via a blood test.

However, if a person does have anemia symptoms, they may notice they get better or go away entirely. The symptoms of anemia include:

  • pale skin
  • fatigue
  • weakness
  • shortness of breath
  • lightheadedness
  • heart palpitations
  • cold hands and feet
  • brittle nails

Certain symptoms of iron deficiency anemia, such as paleness of the skin, usually only occur when hemoglobin levels are very low.

People with symptoms of iron deficiency may feel more energetic and less tired during exercise once iron pills start working. Once the iron level is restored and hemoglobin levels rise, symptoms of iron deficiency resolve.

Children with iron deficiency anemia may also have difficulty with behavior or concentration due to anemia. Sometimes, these effects can be permanent. Doctors are unsure if iron supplementation improves behavioral and cognitive symptoms.

Iron supplements typically begin working within 14 days. Some may notice improvements more quickly than this. To replenish low iron stores in the body, people need to take iron supplements for a minimum of 3 months.

Once iron stores and hemoglobin levels have increased, doctors may recommend that people continue taking iron supplements for another month. This helps increase the stores of iron in the body in case the person’s levels start to drop again.

Whether a person will keep feeling better after stopping iron pills will depend on what was causing their anemia. If they begin getting enough iron in their diet, or they lost blood due to an injury that is now healing, they may not need iron supplements in the future.

If doctors have not identified the cause, though, the anemia may come back.

Doctors recommend taking iron pills at least 30 minutes before a meal, or 2 hours before other medications.

Sometimes, iron pills cause an upset stomach or other side effects. If this occurs, it may help to take iron with a small amount of food. When taking iron with food, avoid the following:

  • milk
  • calcium
  • antacids
  • foods with high fiber content
  • caffeine

Healthcare professionals sometimes recommend taking iron pills with vitamin C or foods that contain vitamin C, such as orange juice. The theory is that this will boost absorption.

However, a study in the Journal of the American Medical Association found that with or without vitamin C, the absorption of iron remains the same.

It is also important to note that the right dosage of iron can vary based on the product. Labels for iron supplements often list two different forms of iron: the main form that the supplement contains, and the elemental form, which is what the body actually absorbs.

Different types of iron supplements have differing amounts of elemental iron. For example, ferrous sulfate contains around 20% of elemental iron, while ferrous fumarate has 33%, and ferrous gluconate has only 12%.

This means the right dose of an iron supplement depends on the type of supplement a person is using. A doctor can help determine the right dosage.

Not everyone taking iron pills will experience side effects, but they can occur, particularly with higher doses. The side effects can include:

Taking a slow release form of iron, taking the pills with food, or taking iron on alternate days may help reduce side effects. Some research suggests that alternate day dosing works as well, if not better than, taking iron every day for people with iron deficiency anemia.

However, if these measures do not help with side effects, a doctor may suggest taking iron pills several times per week instead. This approach may mean it takes longer to restore iron reserves.

Iron pills may not be working if symptoms do not improve. However, since people with iron deficiency anemia can be asymptomatic, it can be challenging to know when iron pills are not working.

Some things that can prevent iron pills from working, or fully resolving symptoms, include:

  • malabsorption, which is when the digestive system cannot effectively absorb nutrients from food or supplements
  • heavy or continuous bleeding, which may mean iron supplements are not enough to restore iron levels
  • certain medications that interfere with iron absorption, such as proton pump inhibitors
  • having more than one nutritional deficiency
  • skipping pills or taking them incorrectly

Doctors can check whether iron pills are working by performing a blood test. If they find the supplements are not working, they may consider a higher dose or a change to iron injections instead of pills.

Alternatively, a doctor may recommend stopping iron supplementation so they can test for other possible causes of low iron levels, which may require different treatments.

If a person is concerned their iron supplement is not working, they should speak with a doctor. People should also speak with a doctor if they are experiencing side effects, as there may be ways to minimize them.

It is important to note that many conditions can cause weakness, low energy, and lightheadedness. Iron pills may not be working if iron deficiency is not the cause.

It is important to seek a diagnosis from a medical professional, rather than trying to self-treat, if a person has not already done so.

Some signs that iron pills are working for iron deficiency anemia include increased energy, less weakness, and less shortness of breath or dizziness.

However, since iron deficiency anemia does not always cause symptoms, people may not display any clear signs that iron pills are or are not working. The best way to be sure is by getting a blood test.

Doctors can monitor iron supplementation to check if it is working. They can also help a person minimize any side effects, and determine the underlying cause of the anemia.