What Happens If an Iron Infusion Doesn’t Work? Plus, Answers to 6 More Iron Supplement FAQs

Iron is an essential mineral for making red blood cells, which carry oxygen throughout your body. If your iron levels drop too low, you can develop a condition called iron deficiency anemia. This causes symptoms such as fatigue, dizziness, and trouble thinking clearly.

To help correct low iron levels, your healthcare team may recommend adding iron-rich foods to your diet or taking an oral iron supplement. In some cases, you may need an iron infusion, which delivers iron directly into your bloodstream. But are iron infusions better than oral iron pills? And what happens if an iron infusion does not work? Here, we’ll answer these and other common questions about iron replacement.

1. What causes low iron levels?

In general, low iron levels are the result of the body either not taking in enough iron or losing iron through blood loss.

Whether you’re not taking in enough iron or losing iron, there could be several underlying causes at play, such as:

• Heavy menstrual bleeding

• Pregnancy, breastfeeding, or having recently given birth

• Recent major surgery or physical trauma

• Health conditions that affect the intestines, such as Crohn’s disease, ulcerative colitis, and celiac disease

• Stomach or intestinal ulcers

• Weight loss surgery

• Following a vegan or vegetarian diet

• Children consuming more than 16 oz of cow’s milk daily

Less common causes of low iron levels include:

• Tumors in the digestive system

• Blood loss from conditions like hemorrhoids or frequent nosebleeds

• Blood loss in the urine (from the kidneys or bladder)

• Frequent blood donations

• Rare conditions that destroy red blood cells in the bloodstream

EXPERT PICKS: WHAT TO READ NEXT

• Iron supplement side effects: Learn which side effects to expect while taking an iron supplement, and when to seek medical care. 

• How long does it take for iron supplements to work? A pharmacist’s answers to this and more FAQs about iron supplements.

• What does taking iron feel like? These first-hand accounts reveal the pros and cons of taking iron supplements.

If your iron levels are low, your healthcare team will likely ask you questions and run blood tests to figure out why. This will help determine the best treatment option for you — more on that later.

When is low iron an emergency?

In some cases, low iron levels can become serious and even life-threatening. That’s because without enough iron, your red blood cells can’t deliver enough oxygen to your brain and organs.

Signs and symptoms of a low iron emergency include:

• Trouble breathing

• Extreme dizziness or fainting

• Severe nausea and vomiting

• Fast or irregular heartbeat

• Heavy or unexplained bleeding

Seek emergency care if you experience any of these symptoms.

2. When do you need an iron infusion vs. an oral iron supplement?

An oral iron supplement is typically the first-choice treatment for low iron levels. In most cases, they’re more affordable and convenient than an iron infusion.

 But your prescriber might recommend an iron infusion if:

• You have very low iron levels and need to raise them quickly

• You have severe symptoms, such as chest pain or extreme fatigue

• You’re living with chronic kidney disease

• You can’t tolerate oral iron side effects (such as stomach pain or constipation)

• Oral iron hasn’t helped after several weeks or months

• Your body can’t absorb oral iron properly (such as after weight-loss surgery or with certain digestive conditions)

• You are pregnant with severe nausea and vomiting

3. What happens if an iron infusion doesn’t work?

As mentioned, if an oral supplement isn’t an option for you, your prescriber may give you an iron infusion to raise your iron levels. Iron infusions are effective for most people.

But what happens if an iron infusion doesn’t work? There are a few reasons this could happen:

• It hasn’t been long enough. It can take up to 9 days for iron levels to go up after an iron infusion.

• You may need another infusion. Some iron infusions require more than one dose to work effectively.

• You’re still losing iron. If your healthcare team isn’t addressing the root cause of low iron levels, even an iron infusion won’t work to keep your iron levels up.

Your healthcare team will work together to fix these issues and get your iron levels back within a safe range.

4. How long does it take for iron supplements to raise iron levels?

Iron supplements usually start working within about a week. But it can take a month or longer for your symptoms to improve.

Your healthcare team will likely check your iron levels periodically to see how well the iron supplement is working. In most cases, you’ll keep taking an oral iron supplement for at least 6 months once your levels return to normal. And in some cases, iron supplements may be a life-long treatment.

5. What are common side effects of taking iron?

Like any supplement or medication, iron has side effects to consider.

Common oral iron supplement side effects include:

• Nausea

• Constipation

• Diarrhea

• Metallic taste

• Black or green stool

• Heartburn

In most cases, you can manage these side effects on your own. Try taking your iron supplement with food or divide it into smaller doses throughout the day. Let your prescriber know if your iron side effects are severe, or if they’re bothering you.

Iron infusions also have side effects to consider, such as:

• Infusion reactions (nausea, low blood pressure, flushing)

• Low phosphate levels

• Severe allergic reactions

Serious iron infusion side effects aren’t common. But a professional will monitor you during your treatment to keep an eye out for signs of an infusion or allergic reaction. 

6. What foods should you avoid when taking iron?

Some foods can block iron absorption if they’re combined with an iron supplement. Dairy products, coffee, and tea are common examples. You should avoid these items for 2 hours before or after taking an oral iron supplement.

Other iron interactions include heartburn medications and nonsteroidal anti-inflammatory drugs (NSAIDs). Give your medication list to your prescriber so they can check for any interactions before you start an iron supplement.

Good to know: Taking an iron supplement with a food or drink that’s high in vitamin C, such as orange juice, can help improve iron absorption.

7. Is it safe to take iron supplements?

Yes — experts consider iron supplements to be safe and effective. But you should only take iron if your prescriber recommends it, and be sure you follow the recommended dosage.

Taking too much iron, or taking an iron supplement if your levels aren’t low, can be dangerous. Symptoms of iron toxicity include blood clots, liver and kidney failure, and even death if left untreated. So you shouldn’t take an iron supplement without speaking to a healthcare professional first. 

In the case of an iron overdose, seek emergency care or call the Poison Control Center at 1-800-222-1222 to figure out the best next steps. Make sure you store iron supplements out of reach of pets and children.

Why trust our experts?

Written by:

Jill Barat, PharmD

Jill Barat, PharmD has nearly 10 years of experience as a pharmacist, including serving as the pharmacist in charge at an independent sterile and non-sterile compounding pharmacy. She also worked as the head of medical content for a telemedicine company.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Sheila McAdoo, PharmD

Sheila McAdoo, PharmD, is a licensed pharmacist in Virginia, New York, and the District of Columbia. She has worked in the pharmacy industry for 12 years and currently works as a community pharmacist.

Our editorial standards

Meet our experts