Hematologist
CION Cancer Clinics
Hydroxyurea for an MPN: side effects and what to expect | CION Cancer Clinics
Most people with polycythaemia vera or essential thrombocythaemia take hydroxyurea for years with mild side effects. The main one to watch is blood counts falling too low, which is why blood tests are frequent at first. Mouth ulcers, dry skin and dark nails are common. A fever, bleeding or a sore that will not heal needs attention. This page explains what to expect and what to report. At CION Cancer Clinics, every leukaemia, MDS and MPN case is reviewed by our haematologist and discussed at a tumour board before a plan is agreed.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What side effects does hydroxyurea usually cause?
- What happens in the first months on hydroxyurea?
- Which side effects are common, and which are less common?
- Which blood test words will you see while on hydroxyurea?
- What do families worry about, and what is actually true?
- Who is hydroxyurea not right for, and what can this page not tell you?
- Common questions about hydroxyurea for an MPN
The short answer
What side effects does hydroxyurea usually cause?
Most people take hydroxyurea for years with side effects that are mild and manageable. The main effect to watch is on your blood counts, which is why you have regular blood tests, especially in the first few months.
What the medicine is doing
Hydroxyurea is a tablet or capsule that slows down the bone marrow, the factory inside your bones where blood cells are made. In polycythaemia vera and essential thrombocythaemia the marrow makes too many cells. The medicine brings red cells and platelets down towards a safer level, which lowers the chance of a clot. You may also see it written as hydroxycarbamide. It is the same medicine under another name.
Why it is called chemotherapy, and why that sounds worse than it is
Hydroxyurea belongs to the chemotherapy family, and families often panic when they read that word on the strip. Taken as a daily tablet for an MPN, it is a very different experience from the drip chemotherapy used for other cancers. Most people keep working, travelling and eating normally. Hair loss is uncommon and usually limited to some thinning.
Your haematologist sets and adjusts the amount you take. Never change it, skip it or stop it on your own, even if you feel well.What to expect
What happens in the first months on hydroxyurea?
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Before the first tablet
You will have a full blood count and usually kidney and liver tests. Tell the team about every medicine you take, and whether pregnancy is possible for you or your partner.
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The early weeks
Blood tests are frequent at the start, because this is when counts can drop faster than expected. Some people notice a mild upset stomach or feel more tired than usual for a while.
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Finding the right amount
Your haematologist adjusts the amount step by step, looking at your haematocrit, platelets and white cells together. It can take a few months to settle, and changes in this period are normal.
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The settled phase
Once counts are steady, blood tests become less frequent. You keep taking the tablets daily and attend reviews. Any new skin sore or mouth ulcer is worth mentioning at each visit.
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The long term
Many people stay on it for many years. The team checks your skin, your counts and how you feel, and reviews whether hydroxyurea is still the right medicine for you.
Not sure whether this applies to you?
Ask an oncologistSide effects
Which side effects are common, and which are less common?
Most people have one or two of these, not all of them. Tell your team about any of them rather than putting up with it quietly.
Lower blood counts
This is the effect the medicine is meant to have, but counts can drop too far. Low white cells raise the chance of infection. Low platelets can cause easy bruising or bleeding gums.
Mouth and stomach
Mouth ulcers, a mild upset stomach, loose motions or a reduced appetite. These often settle over time or with small changes the team suggests.
Skin and nails
Dry skin, darker patches, and dark lines or bands on the nails are common and harmless. Sun sensitivity can increase.
Mention at your next visit
- A new mole or a patch that changes
- A rough, scaly spot on sun-exposed skin
Leg ulcers
Less common, but important. A painful sore that will not heal, often near the ankle, needs to be seen. It can be linked to the medicine and the team may consider an alternative.
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What cannot wait until your next appointment
A fever, shivering, a sore throat that is getting worse, bleeding that will not stop, blood in the urine or black stools, or many new bruises can mean your counts have dropped too low. Go to the nearest emergency department the same day, or call 108, and tell them you take hydroxyurea for an MPN. Then let your haematology team know.
On your report
Which blood test words will you see while on hydroxyurea?
- Haematocrit (HCT or PCV)
- The share of your blood made up of red cells. In polycythaemia vera this is the main number the treatment aims to control.
- Platelets
- The cells that help blood clot. In essential thrombocythaemia this is the number the medicine brings down.
- WBC and neutrophils
- White cells, and the main infection-fighting type among them. A low result is the one your team watches most closely.
- MCV
- The average size of your red cells. It usually rises on hydroxyurea. On its own this is expected and is not a sign of harm.
- Flagged high or low
- Reference ranges differ between laboratories. A single result is read alongside your symptoms and your earlier tests, not on its own.
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Commonly believed
What do families worry about, and what is actually true?
"It is chemotherapy, so it will make him very ill."
Hydroxyurea for an MPN is a daily tablet, usually taken at home. Most people carry on with ordinary life. It is watched closely through blood tests so that problems are picked up early.
"Her counts are normal now, so she can stop the tablets."
Normal counts usually mean the medicine is working. Stopping on your own lets the counts rise again, and the clot risk comes back with them. Any change is decided by the haematologist.
"Hydroxyurea turns an MPN into leukaemia."
This worry is common. Large studies have not shown a clear link for most people, though the question is still followed. Your haematologist can explain how it applies to your own disease.
"The dark nails mean the medicine is poisoning him."
Darker nails and skin are a known, harmless effect. They are not a sign of damage to the liver, kidneys or blood. They are still worth mentioning so the team can note them.
Being straight with you
Who is hydroxyurea not right for, and what can this page not tell you?
Hydroxyurea is not usually offered to someone who is pregnant, planning a pregnancy or breastfeeding, because it can harm a developing baby. Men and women taking it are generally advised to use reliable contraception. If you are thinking about a family, say so early, because other options exist.
When another medicine may be chosen
Some people cannot take it, because counts fall too far, leg ulcers develop, or it simply does not control the disease. Younger people are sometimes offered an interferon medicine instead. Others may move to ruxolitinib. These decisions depend on age, symptoms, other illnesses and what has been tried before.
What this page cannot tell you
It cannot tell you whether your side effects are from hydroxyurea or from something else, or whether your amount is right. Only your blood results, read by the team treating you, can answer that. Write down any new symptom with the date it started and bring the list to your review.
If you would like a second look at your treatment plan, CION's haematology team can review your reports and your blood test history with you.Questions we are asked
Common questions about hydroxyurea for an MPN
Will I lose my hair on hydroxyurea?
Hair loss is uncommon. A few people notice some thinning over time, but the complete hair loss people link with drip chemotherapy is not expected. If thinning bothers you, mention it at your review. The team can check whether something else, such as thyroid problems or low iron, is adding to it.
How long will I need to take it?
For most people it is a long-term medicine, often taken for years. It controls the counts while you take it rather than removing the disease. Your haematologist reviews at every visit whether it is still working, still suits you, and whether a different option has become more sensible.
I missed a dose. What should I do?
Do not take extra to make up for it. Follow the written instructions you were given, and if you are unsure, call your haematology team or ask your pharmacist. An occasional missed dose is rarely a crisis, but tell the team if it keeps happening, because it can affect your counts.
Can I drink alcohol or take other medicines with it?
Small amounts of alcohol are usually not a problem, but ask your own team. Always tell any doctor, dentist or pharmacist that you take hydroxyurea. Some medicines, including certain HIV medicines and some vaccines, need extra care. Avoid live vaccines unless your haematologist agrees.
Should family members handle the capsules?
Anyone who is pregnant should avoid handling the capsules. Others can wash their hands after touching them, or wear gloves. Keep the medicine in its box, away from children, and do not open or crush the capsules. Ask the pharmacy how to return any you no longer need.
Does it raise the risk of skin cancer?
Long-term use is linked with a higher chance of some skin cancers, mostly on sun-exposed skin. Cover up in strong sun, use sunscreen, and look at your skin every few months. Show the team any new or changing patch. Most skin cancers of this kind are very treatable when found early.
My MCV is high on the report. Is that a problem?
A raised MCV, meaning larger red cells, is an expected effect of hydroxyurea and on its own is not a warning sign. Your team may still check your vitamin B12 and folate if other results change. Reference ranges differ between laboratories, so compare results from the same lab where you can.
Is hydroxyurea covered by Aarogyasri or insurance?
Cover for long-term tablets and blood tests varies by scheme and policy. Aarogyasri, CGHS, ECHS, EHS, PM-JAY and cashless insurance each have their own rules, and those rules change. Call the helpline with your card details and we will check what your current cover includes before your next review.
Your Haematologist
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- Cancer Research UK — Hydroxycarbamide (Hydrea)
- Macmillan Cancer Support — Hydroxycarbamide
- Leukemia & Lymphoma Society — Polycythemia vera
- NHS — Polycythaemia
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Polycythaemia Vera ExplainedWhat the condition is and why counts are controlledMPN Monitoring: Which Tests and How OftenThe blood tests you will have while on treatmentVenesection: Why Blood Is Removed as TreatmentThe other main way haematocrit is controlledWill My MPN Turn Into Leukaemia?The worry many families have about long-term treatment
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