Why Are Iron Supplements Avoided in Polycythemia Vera?

It is incredibly frustrating to feel exhausted, look at your lab results, see that you are iron deficient, and be told by your doctor not to take an iron supplement. For most people, low iron means they need to take an iron pill. However, in polycythemia vera (PV), iron deficiency is a very common consequence of your treatment—and managing it requires a delicate balance.

The primary goal of PV treatment is not to make you iron deficient, but rather to control your hematocrit (the percentage of your blood made up of red blood cells). For many adults with PV, guidelines recommend maintaining a hematocrit below 45% ^[1]. This target is critical because a higher hematocrit thickens the blood and significantly increases your risk of dangerous blood clots, heart attacks, and strokes ^[2].

Therapeutic phlebotomies remove whole blood, which lowers your hematocrit but also removes iron. Because PV is driven by a bone marrow disorder (often involving a JAK2 mutation) that constantly signals the body to make more red blood cells, restricting iron limits the marrow’s ability to overproduce these cells ^[3][4].

If you take an iron supplement, you provide your bone marrow with the exact building blocks it needs to produce red blood cells again ^[5]. This can cause your hematocrit levels to rise, sometimes rapidly, undoing the protective effects of your phlebotomy treatments and increasing your risk of blood clots ^[6][7].

The Real Toll of Iron Deficiency

While low iron helps constrain red blood cell production, the symptoms you are experiencing are very real. Iron deficiency can cause severe fatigue, lethargy, “brain fog” (impaired concentration), and restless legs ^[4][8]. These symptoms can severely impact your quality of life, and it is completely valid to want relief.

It is also important to understand how iron deficiency affects your lab results. A lack of iron causes red blood cells to become smaller (a condition called microcytosis) ^[9]. Because smaller cells take up less space, your hematocrit percentage might look relatively low even if your actual number of red blood cells is still very high. Correcting the iron levels can plump the cells back up, suddenly revealing a much higher hematocrit ^[6].

Urgent Safety Warning: Never assume that all your symptoms are just from low iron. In patients with PV, dizziness, vision changes, new or severe headaches, chest pain, shortness of breath, or sudden weakness/numbness can be signs of hyperviscosity (dangerously thick blood) or a blood clot (like a stroke or heart attack). Seek emergency medical care immediately if you experience these warning signs.

What You Can Do Instead

You should never start taking an over-the-counter iron supplement, multivitamin with iron, or prescription iron on your own without direct supervision from your hematologist.

However, you do not have to simply suffer in silence through debilitating exhaustion. If your symptoms are severely impacting your daily life, talk to your care team about your options:

• Investigate Other Causes: Iron deficiency shouldn’t automatically be blamed solely on phlebotomy, especially if it worsens suddenly. Since many PV patients take aspirin, your doctor may need to rule out other causes of low iron, such as hidden gastrointestinal bleeding.
• Supervised, Cautious Iron Replacement: In specific cases where iron deficiency symptoms are severely disabling, a hematologist may weigh the risks and benefits and prescribe a carefully monitored, strictly limited course of iron. This requires very close tracking of your blood counts to ensure your hematocrit does not rise dangerously.
• Cytoreductive Therapies: If frequent phlebotomies are causing unbearable iron deficiency, your doctor may discuss adding or switching to a cytoreductive therapy (such as hydroxyurea or interferon). These medications are selected based on your age, symptoms, and clot risk, and they slow down the bone marrow directly, potentially reducing your need for phlebotomies ^[10].
• Targeted Therapies: For adults whose PV is not adequately controlled by or who cannot tolerate hydroxyurea, medications like ruxolitinib may be considered. In clinical studies, this targeted therapy has helped control blood counts and improved symptoms like fatigue and brain fog for some patients ^[8].
• Emerging Clinical Trials: Researchers are currently studying investigational drugs, such as rusfertide (a hepcidin mimetic). In early clinical trials, these experimental therapies aim to mimic the body’s natural iron-regulating hormones to keep hematocrit controlled without the need for constant phlebotomies ^[11][12]. Your doctor can tell you if you are eligible for any ongoing trials.