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Hyperviscosity syndrome in Waldenström: symptoms and what to do | CION Cancer Clinics
Hyperviscosity syndrome is an emergency. If someone with Waldenström has sudden blurred vision, nosebleeds or bleeding gums that will not stop, a severe headache, confusion or breathlessness, call 108 or go to the nearest emergency department now. The blood has become too thick with IgM protein to flow properly. Plasma exchange thins it quickly, and the lymphoma is then treated to keep it from returning. At CION Cancer Clinics, our haematology team plans myeloma and lymphoma care with you, discussed at a tumour board and explained in plain words.
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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 is hyperviscosity syndrome, and why is it an emergency?
- What are the symptoms of hyperviscosity syndrome?
- What happens at the emergency department?
- Which words on the report relate to thick blood?
- What do families get wrong about thick blood?
- How do you lower the chance of it happening again?
- Common questions about hyperviscosity syndrome
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Do this first
If someone with Waldenström macroglobulinaemia, or a high IgM or paraprotein level, has sudden blurred or lost vision, a nosebleed or bleeding gums that will not stop, a severe headache, confusion, fits, drowsiness, chest pain or breathlessness, call 108 or go to the nearest emergency department now. Take the latest blood report and say the words "Waldenström" and "possible hyperviscosity". Do not wait for the next clinic visit, and do not accept a blood transfusion at a local clinic before a haematologist has been told about the diagnosis.
The short answer
What is hyperviscosity syndrome, and why is it an emergency?
Hyperviscosity syndrome means the blood has become too thick to flow properly through the smallest blood vessels. It is an emergency because thick blood can starve the eyes, brain, heart and lungs of oxygen within hours to days, and it can cause serious bleeding.
Why it happens in Waldenström
Waldenström macroglobulinaemia is a slow-growing lymphoma. Its cells make large amounts of an antibody protein called IgM. IgM molecules are very big and sticky. When there is a lot of it, the liquid part of the blood turns thick, rather like syrup instead of water. Thick blood moves slowly, and the tiny vessels at the back of the eye and in the brain are the first to suffer.
Who is most at risk
The risk rises as the IgM level rises, but there is no single number at which everyone gets symptoms. Some people feel unwell at a lower level, and others feel well at a higher one. People with a rapidly rising IgM, those with heart problems, and older people are more likely to be affected. It can also happen with myeloma, though less often.
Laboratory reference ranges differ, and a single IgM result is always read with your symptoms and repeat tests.Not sure whether this applies to you?
Ask an oncologistWarning signs
What are the symptoms of hyperviscosity syndrome?
Symptoms usually fall into four groups. Any one of them, in someone with a high IgM, needs same-day assessment.
Bleeding
Thick protein coats the platelets and stops them working, even when the platelet count looks normal.
Look for
- Nosebleeds that keep returning
- Bleeding gums
- Unusually heavy bleeding from small cuts
Eyes
The fine vessels at the back of the eye swell and may bleed. An eye doctor can often see this directly.
Look for
- Blurred or double vision
- A dark patch in the vision
- Sudden loss of sight in one eye
Brain and nerves
Slow blood flow to the brain causes symptoms that families often mistake for old age or tiredness.
Look for
- Headache, dizziness, ringing in the ears
- Confusion or unusual sleepiness
- Unsteady walking, fits
Heart and lungs
The heart works harder to push thick blood around the body, and fluid may collect.
Look for
- Breathlessness, especially lying flat
- Swelling of the ankles
- Chest pain
At the hospital
What happens at the emergency department?
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Quick checks
Blood pressure, oxygen level and a short look at the nerves and eyes. Tell the team straight away about the Waldenström diagnosis and show the most recent IgM result.
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Blood tests
Blood counts, kidney tests, the IgM level and, where available, a test of how thick the serum is. An eye examination with drops looks at the vessels at the back of the eye.
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Supportive care
Fluids through a drip may be given carefully. Doctors avoid giving a blood transfusion quickly, because extra red cells can make thick blood even thicker.
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Plasma exchange
Plasma exchange, also called plasmapheresis, is the main emergency treatment. A machine removes the thick liquid part of the blood and replaces it with a safe fluid. It works fast, often over one or two sessions, but only at centres with the equipment. CION does not do this in-house and will coordinate an urgent transfer if it is needed.
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Treatment of the lymphoma
Plasma exchange buys time. It does not stop the lymphoma making more IgM, so treatment of the Waldenström itself is started or changed by the haematologist soon afterwards.
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On your report
Which words on the report relate to thick blood?
- IgM
- A large antibody protein. In Waldenström the lymphoma cells make too much of one kind of it.
- Paraprotein or M-protein
- The single abnormal protein made by the lymphoma cells. Its level is tracked over time to see how the disease is behaving.
- Serum viscosity
- A measure of how thick the liquid part of the blood is. Not every laboratory offers it.
- Plasmapheresis
- Removing plasma, the liquid part of the blood, by machine and replacing it.
- Fundoscopy
- An eye examination that looks at the blood vessels at the back of the eye.
- Cryoglobulins
- Proteins that clump in the cold. They can cause similar symptoms, especially in the fingers and toes.
Commonly believed
What do families get wrong about thick blood?
"His eyesight is going because of age. We will see the eye doctor next month."
In someone with Waldenström, new blurred vision can be the first sign of thick blood. It needs checking the same day, because bleeding at the back of the eye can cause lasting damage.
"She looks pale and weak, so a blood transfusion will help."
Low haemoglobin is common in Waldenström, but a fast transfusion can make thick blood worse. Transfusion decisions belong to the haematologist, who may first lower the IgM.
"Drinking lots of water will thin the blood out."
Staying well hydrated is sensible, but water cannot remove the extra protein. Only plasma exchange and treatment of the lymphoma lower the IgM.
"A blood thinner tablet will fix thick blood."
Blood thinners treat clots, not thick protein. In this situation they can raise the chance of bleeding. Never start or stop one on your own.
After the emergency
How do you lower the chance of it happening again?
Once the blood has been thinned by plasma exchange, the aim is to control the lymphoma so the IgM stays lower. Your haematologist chooses the treatment based on your age, fitness, kidney function and any other illnesses. Options often include rituximab-based combinations or a BTK inhibitor such as ibrutinib or zanubrutinib, a tablet that blocks a signal the lymphoma cells rely on.
The rituximab flare
When rituximab is started with a high IgM, the level can briefly rise before it falls. This is called an IgM flare. For that reason, teams sometimes lower the IgM first or hold rituximab back at the start. Ask your team whether this applies to you. Do not change or skip a dose yourself.
What this page cannot tell you
It cannot tell you whether your own symptoms are from thick blood or from something else, such as infection or low haemoglobin. It cannot give a safe IgM number for you. Those answers need an examination and blood tests. If you are unsure, treat the symptom as urgent and get it checked.
Keep a copy of your latest IgM result and a short note of your diagnosis on your phone, so any emergency doctor can see it.Questions we are asked
Common questions about hyperviscosity syndrome
Is hyperviscosity syndrome life-threatening?
It can be, if it is not treated quickly. Thick blood can lead to bleeding in the eyes or brain, fits, heart strain and breathing trouble. The good news is that plasma exchange works fast once it is started. That is why same-day care matters more than anything else on this page.
At what IgM level does hyperviscosity start?
There is no single level that applies to everyone. Symptoms become more likely as IgM rises, but some people have symptoms at a lower level and others stay well at a higher one. Your haematologist watches the trend over time, together with how you feel, rather than one number.
Which hospital should we go to in an emergency?
Go to the nearest emergency department first, or call 108. Do not travel a long distance to reach a particular hospital while symptoms are severe. Once stable, the doctors can arrange transfer to a centre that offers plasma exchange if it is needed. Call your haematology team to let them know.
Can hyperviscosity happen without Waldenström?
Yes, though less often. It can occur in myeloma, especially types that make IgA, and with very high white cell counts in some leukaemias. The treatment differs by cause. Whatever the cause, the warning signs of bleeding, vision change and confusion need the same urgent attention.
Does plasma exchange hurt, and is it safe?
It feels similar to a long blood donation. A needle or a thin tube is placed in a vein, and the machine runs for a few hours. Some people feel tingling around the lips or light-headed. Staff watch you throughout. Serious problems are uncommon at experienced centres.
My father is on watch and wait. Should we worry?
Most people on watch and wait never develop hyperviscosity. Keep the scheduled blood tests, because a rising IgM is one of the signals that treatment should start. Learn the warning signs on this page, and share them with whoever lives with him, so nobody waits if they appear.
Can we have eye surgery or a procedure with a high IgM?
Tell every doctor about the Waldenström diagnosis before any procedure, including cataract surgery or dental work. Thick blood and poorly working platelets can raise bleeding risk. The surgeon and haematologist should agree on timing together. Never stop any medicine before a procedure without their advice.
Is plasma exchange covered by Aarogyasri or insurance?
Emergency care for a blood cancer is often covered by Aarogyasri, PM-JAY, CGHS, ECHS, EHS or cashless insurance, but rules differ by scheme and hospital. Do not delay emergency care to check cover. Once stable, ask the hospital billing desk to confirm your current entitlement.
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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
- American Cancer Society — Waldenström macroglobulinemia
- Leukemia & Lymphoma Society — Non-Hodgkin lymphoma
- National Cancer Institute — Lymphoma
- Cancer Research UK — Non-Hodgkin lymphoma
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
Indolent LymphomaThe full guide to slow-growing lymphomas, including WaldenströmWatch and Wait in Follicular LymphomaWhat active monitoring involves and when treatment startsIndolent Lymphoma Surveillance ScheduleHow often blood tests and reviews are doneBlood cancer guideAn overview of blood cancers and how they are treated
Talk to us
Worried about a rising IgM?
In an emergency, call 108 first. For a non-urgent review of your reports, CION's haematology team can go through them with you. One helpline serves every CION centre.