If you have a certain kind of anemia, your doctor might suggest Injectafer as a treatment option for you. It’s a prescription drug used to treat iron deficiency anemia (IDA) in adults and some children who:

  • have taken iron supplements by mouth but have not had improvement in their IDA, or
  • can’t take iron supplements by mouth due to side effects

Injectafer is also used to treat IDA in adults with long-term kidney disease who don’t need dialysis.

The active ingredient in Injectafer is ferric carboxymaltose. (An active ingredient is what makes a drug work.)

Injectafer comes as a liquid solution that your doctor or another healthcare professional will give you through either an intravenous (IV) infusion or a slow IV injection.*

If your doctor prescribes Injectafer, you’ll likely use it short term until your iron levels are at a healthy level.

For more information about Injectafer, including details about its uses, see this in-depth article on the drug.

Like other drugs, Injectafer can cause mild to serious side effects. Keep reading to learn more.

*With an IV infusion, the drug is given as a slow drip into your vein over time. With slow IV injection, the drug is given as a single, slow injection into your vein. IV infusions usually take longer than slow IV injections.

Some people may experience mild to serious side effects during their Injectafer treatment. Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

Many common side effects of Injectafer are mild. Examples that have been reported with this drug include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And don’t stop using Injectafer unless your doctor recommends it.

Injectafer may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Injectafer, visit MedWatch.

It’s possible that Injectafer may cause serious side effects in some people, but these are rare. Serious side effects that have been reported in the drug’s studies include:

If you develop serious side effects while taking Injectafer, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.

Injectafer can be used to increase iron levels in children ages 1 year and older with iron deficiency anemia (IDA). Many side effects of Injectafer in children are similar to those seen in adults, but a few are different in children.

In Injectafer studies, the following side effects were more common in children using Injectafer than they were in adults:

Side effects seen in children using Injectafer but not in adults include:

Get answers to some frequently asked questions about Injectafer’s side effects.

Is the risk of side effects higher with Injectafer infusions than with slow intravenous (IV) injections of the drug?

Not really. Most side effects from Injectafer should be the same whether you receive the drug through an intravenous (IV) infusion or a slow IV injection.

IV infusions usually take longer than slow IV injections. It’s also easier to control the rate at which you receive the drug with an IV infusion. So your risk of injection site reactions may be lower with an IV infusion than with a slow IV injection. This is because receiving IV medications too fast increases your risk of certain site reactions, such as skin darkening at the injection site.

Does Injectafer cause any long-term side effects?

Yes, but it’s not common. Skin darkening at the infusion or injection site is a rare side effect reported in Injectafer studies. This happens when a drug that’s given by intravenous (IV) infusion or injection leaks into the skin surrounding the injection site. In some cases, this side effect can be long term.

It’s important to let your doctor or a healthcare professional know right away if you have pain or severe discomfort at your Injectafer infusion or injection site. They can check for drug leakage and address the issue quickly to minimize long-term skin darkening.

Does Injectafer cause weight gain?

No. Weight gain was not a side effect in Injectafer studies. But it’s possible that your appetite may increase as a result of your anemia improving from Injectafer. If this is the case, you might gain weight after being treated with this drug.

Talk with your doctor if you have concerns about weight changes with Injectafer.

Learn more about some of the side effects Injectafer may cause.


It’s possible to get diarrhea from Injectafer, but it wasn’t a common side effect in studies. Symptoms of diarrhea can include:

What might help

Over-the-counter (OTC) diarrhea treatments, such as Imodium (loperamide), can help relieve mild diarrhea. But be sure to check with your doctor or pharmacist before taking OTC medications. They’ll let you know if they’re safe with other drugs you take or conditions you have.

Contact your doctor if you have severe diarrhea or if it’s not relieved with OTC medication. They can recommend additional ways to manage this condition.

High blood pressure

Increased blood pressure was among the more common side effects in Injectafer studies. This side effect is more likely to happen immediately after receiving your dose of the drug. In most cases, blood pressure increases are mild and go away within 30 minutes.

In rare cases, blood pressure increases from Injectafer can be severe. Symptoms of severe high blood pressure can include:

What might help

Your doctor or another healthcare professional will monitor your blood pressure for about 30 minutes after you receive your Injectafer dose.

Let your doctor know if you have symptoms of severe high blood pressure after receiving Injectafer. If your blood pressure is too high, they’ll provide treatment.

Low blood phosphorus level

Injectafer can cause a low blood phosphorus level. (Phosphorus is an electrolyte your body uses for energy production and proper nerve function.) This side effect was somewhat common in studies of the drug. It has also been reported by people receiving Injectafer since the drug was approved for use. And most people’s phosphorus level went back to normal within 3 months.

You may have an increased risk of developing a low blood phosphorus level from Injectafer if you:

You may not have symptoms if you have a mild to low phosphorus level. But in some people, low blood phosphorus can be severe and includes symptoms such as:

What might help

Your doctor will do blood tests to check your phosphorus level during your Injectafer treatment. If your level is too low, they may prescribe a treatment other than Injectafer for your condition. If needed, your doctor will provide treatment to increase your phosphorus level.

Let your doctor know if you have symptoms of low blood phosphorus level. They’ll determine whether it’s safe for you to continue using Injectafer.

Injection or infusion site reaction

Injection or infusion site reaction was one of the more common side effects reported in studies of people receiving Injectafer. These are reactions that occur around the area where you receive your Injectafer injection or infusion and can include:

  • pain at the injection or infusion site
  • fluid leaking out under your skin into the area around the injection or infusion
  • darkening of the skin around the infusion or injection site

Fluid leaking into the area around the injection or infusion site can lead to skin darkening around the site, which can be long term.

What might help

Your doctor or another healthcare professional will give you your Injectafer dose through an intravenous (IV) infusion or a slow IV injection. This will help reduce your risk of injection or infusion site reaction.

Let your doctor know right away if you experience severe pain or discomfort while receiving your Injectafer dose.

Allergic reaction

Like most drugs, Injectafer can cause an allergic reaction in some people. This side effect was reported in Injectafer studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Injectafer, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Injectafer, they may have you switch to a different treatment.

Keeping track of side effects

During your Injectafer treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Injectafer affects you. They can then use this information to adjust your treatment plan if needed.

Injectafer may not be right for you if you have certain medical conditions. (This is known as drug-condition interaction.) Other factors may also affect whether Injectafer is a good treatment option for you. Talk with your doctor about your health history before starting this treatment. Below are several factors to consider.

Low blood phosphorus level. Injectafer can cause a low level of blood phosphorus. Your risk is higher if you already have trouble absorbing phosphorus and certain other vitamins or if you take drugs that may lower your phosphorus level. Talk with your doctor about your health history, including all the drugs you take, before you start Injectafer treatment.

Allergic reaction. If you’ve had an allergic reaction to Injectafer or any of its ingredients, your doctor will likely not prescribe Injectafer. Ask them about other medications that might be better options for you.

High blood pressure. Using Injectafer can temporarily increase your blood pressure. If you already have high blood pressure, this medication may cause it to become severe. Let your doctor know if you have high blood pressure or take medication to treat it before starting Injectafer.

Alcohol and Injectafer

There are no known interactions between alcohol and Injectafer. But consuming large amounts of alcohol can worsen or cause anemia in some people. This is because alcohol can interfere with your body’s ability to absorb vitamins needed to make red blood cells.

Talk with your doctor to learn how much alcohol is safe to consume while you’re using Injectafer.

Pregnancy and breastfeeding while taking Injectafer

It’s not known whether it’s safe to use Injectafer during pregnancy. In studies of the drug, there were no problems reported in pregnant people taking Injectafer or their children. But these studies were not designed to determine whether Injectafer is safe to use during pregnancy.

Untreated iron deficiency anemia can increase the risk of pregnancy-related issues, such as preterm delivery and low birth weight of your infant. In addition, having an allergic reaction to Injectafer infusions while pregnant could cause the fetus to have a slow heart rate. (To learn more about allergic reaction with Injectafer, see the “Side effects explained” section above.)

Let your doctor know if you’re pregnant or planning to become pregnant before starting Injectafer. They can help you decide which anemia treatment is right for you.

Injectafer passes into breast milk, but it’s not known if it’s safe to take this medication while breastfeeding. In studies, breastfed infants of people using Injectafer had side effects such as constipation and diarrhea. But it’s not clear whether these side effects were due to this drug.

If you’re breastfeeding or planning to do so, talk with your doctor before starting Injectafer. They’ll help you decide whether this treatment is right for you.

Like many medications, Injectafer can cause side effects in some people. The most common side effects of this drug are mild and go away on their own. But some side effects may be severe and require medical care. Talk with your doctor before starting Injectafer treatment to learn what to expect from this drug and ways to manage side effects. Here are examples of questions you may want to ask:

  • Does my risk of high blood pressure depend on the dosage I use?
  • How do the side effects of Injectafer compare with those of iron tablets?
  • Am I at an increased risk of side effects if I have kidney or liver problems?
  • Would increasing my infusion time reduce my risk of side effects?

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.