Hyperviscosity Syndrome: A Comprehensive Guide to Symptoms, Causes, and Clinical Management
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
Hyperviscosity syndrome (HVS) is a condition in which the blood thickens and cannot flow freely through blood vessels. Untreated, it can block arteries and lead to organ failure. Symptoms include nosebleeds or bleeding gums, blurred vision and headache or dizziness. Its most common cause is Waldenström macroglobulinemia. Severe cases are treated with plasmapheresis plus treatment of the underlying disease. [1]
What the research says
Plasmapheresis lowered IgM by about 44% in one small study. In 10 patients with untreated Waldenström macroglobulinemia and hyperviscosity syndrome (or IgM of 4,000 mg/dL or more), the median IgM level fell from 5,174 to 2,900 mg/dL after plasmapheresis. No patient had an IgM flare or a bleeding adverse event. (Ito et al., Therapeutic Apheresis and Dialysis, 2024)
The eyes can give the diagnosis away. Two recent reviews describe hyperviscosity syndrome as an emergency and stress that a fundoscopic (eye-back) exam is important. Bilateral nasal bleeding plus neurologic and eye symptoms should raise suspicion, and plasma exchange is the main treatment for severe cases, followed by treating the underlying cause to prevent recurrence. (Bey & Qdaisat, Emergency Medicine Clinics of North America, 2025; Debureaux et al., La Revue de Médecine Interne, 2024)
What is hyperviscosity syndrome?
Hyperviscosity syndrome occurs when certain medical conditions make your blood too thick to flow through your blood vessels. Under normal conditions, blood moves smoothly through arteries and veins to deliver oxygen and nutrients to the organs. [1] When an underlying condition causes abnormal red blood cells or too many red cells, white cells, or platelets, the blood becomes thick and sluggish. In other cases, abnormal proteins clump and thicken it. This is a medical emergency because thick blood can block arteries and lead to organ failure if circulation is not restored. [1]
The triad of hyperviscosity and other symptoms
Healthcare providers recognize the syndrome by a group of symptoms called the "triad of hyperviscosity." [1]
Symptom category | Specific signs |
Bleeding | Chronic nosebleeds and bleeding gums. |
Vision | Blurred vision or other vision problems. |
Neurological | Headache, dizziness, vertigo, and seizure-like symptoms such as uncontrollable movements or staring. |
Other symptoms may include skin that looks reddish or darker than usual, chest pain, difficulty walking, hearing problems, and shortness of breath. [1]
Root causes: from blood cancers to autoimmune disorders
Waldenström macroglobulinemia, a rare type of blood cancer, is the most common cause. In this lymphoma, malignant cells make large amounts of IgM antibody, which thickens the blood. [1][5] Many other conditions can also cause hyperviscosity syndrome. [1]
Common medical triggers
Blood cancers: Multiple myeloma, acute myeloid leukemia, and myelodysplastic syndrome. [1]
Autoimmune diseases: Lupus, rheumatoid arthritis, and Sjögren's syndrome. [1]
Blood disorders: Essential thrombocytosis, leukemia, and polycythemia (too many red blood cells). [1]
Other conditions: Chronic hypoxia (lack of oxygen to tissues), cryoglobulinemia (abnormal proteins that clump in the blood), and paraneoplastic syndromes (an immune reaction to cancer that damages healthy cells). [1]
Diagnosis and clinical testing
When hyperviscosity syndrome is suspected, providers review your health history and symptoms, asking specifically about unusual bleeding, vision problems, and dizziness or vertigo. They may order several blood tests. [1] An eye exam that looks at the back of the eye (fundoscopy) is also important. [2][3]
Serum viscosity: Measures how thick the blood serum is and how fast it flows. [1]
Complete blood count (CBC): Measures blood cell and plasma levels. [1]
Creatinine and liver function tests: Check the kidneys and liver, which are affected when blood is thick. [1]
Arterial blood gas (ABG): Measures oxygen and carbon dioxide levels in the blood. [1]
Bilirubin test: Checks bilirubin, which the body makes when red blood cells break down. [1]
Management and treatment pathways
Treatment depends on the condition causing the thick blood. The immediate goal is to bring viscosity down and prevent organ damage. [1]
Partial plasma exchange (plasmapheresis)
In severe cases, a provider may perform a partial plasma exchange, in which the thickened plasma is removed and replaced with a healthy substitute. People who have plasma exchange typically recover within a few hours. [1] Plasma exchange is considered the main treatment for severe cases. [3]
Long-term outlook
Prompt treatment typically controls hyperviscosity syndrome, but you will need ongoing treatment for the underlying condition. Otherwise, the syndrome can come back. [1] Ask your healthcare provider which symptoms to watch for if you have a blood cancer, blood disorder, or autoimmune disease that raises your risk. [1]
Conclusion
Hyperviscosity syndrome is a serious and potentially life-threatening problem, but early recognition makes a real difference. If you have a blood disorder or autoimmune disease, stay alert to the triad of bleeding, vision changes, and neurological symptoms such as headache and dizziness, and contact your healthcare provider promptly if they appear. [1]
Take charge of your health. For more guides on blood health and managing chronic conditions, visit Rinnit.com.
Frequently Asked Questions
Is hyperviscosity syndrome always a medical emergency?
Yes. Thick blood can block arteries and lead to organ failure, so any suspicion of hyperviscosity syndrome needs immediate medical evaluation. [1]
Can I prevent hyperviscosity syndrome?
Prevention means managing the underlying condition. If you have a blood disorder, blood cancer, or autoimmune disease, following your treatment plan is the best way to keep your blood from thickening. [1]
Does thick blood cause a stroke?
Thick blood can block blood flow to organs, including the brain, which is why neurological symptoms such as severe headache, dizziness, vertigo, or seizure-like movements need emergency care. [1]
How long does plasma exchange take to work?
The length of a session varies, but people who have plasma exchange typically recover within a few hours. [1]
Are the symptoms of HVS permanent?
With timely treatment, many people recover fully. Delayed treatment raises the risk of lasting organ damage. [1]
Can children get hyperviscosity syndrome?
Most cases involve adults with blood cancers or autoimmune disease, but the conditions that thicken blood can affect people of different ages, including newborns with too many red blood cells (polycythemia).
Why does thick blood cause vision problems?
Thick blood moves poorly through the tiny vessels at the back of the eye, which can cause blurred vision or other vision changes. This is why an eye exam is useful in diagnosis. [1][2]
Is HVS a type of cancer?
No. It is a syndrome, a set of symptoms. However, it is often caused by blood cancers such as Waldenström macroglobulinemia, multiple myeloma, or leukemia. [1]
Can I manage HVS at home?
No. It needs urgent medical care, including blood tests and sometimes plasma exchange, which are done in a medical setting.
What is the most common sign of HVS?
The triad of bleeding (nosebleeds or bleeding gums), vision problems, and neurological symptoms (headache, dizziness, vertigo) is the hallmark. [1]
Does thick blood affect the liver?
Yes. Liver function tests are part of the work-up because the liver is one of the organs affected by thick blood. [1]
What happens if HVS is left untreated?
Thick blood can block arteries and reduce blood flow to vital organs, leading to organ failure. [1]
Is plasma exchange painful?
Plasma exchange uses a machine to remove and replace plasma. Your care team can explain what to expect and how it is made comfortable. Most people recover within a few hours. [1]
How often will I need a viscosity test?
How often you need a viscosity test depends on your underlying condition and your doctor's plan. People with HVS stay under the close care of a specialist, usually a hematologist.
Can stress cause hyperviscosity syndrome?
No. HVS is caused by physical changes in the blood, such as too many cells or abnormal proteins, not by emotional stress. [1]
References
Cleveland Clinic. Hyperviscosity Syndrome. Cleveland Clinic. Last updated April 6, 2026. https://my.clevelandclinic.org/health/diseases/23938-hyperviscosity-syndrome
Bey T, Qdaisat A. Hyperviscosity Syndrome: An Oncologic Emergency. Emerg Med Clin North Am. 2025;43(3):445-452. PMID 40610061. https://doi.org/10.1016/j.emc.2025.03.001
Debureaux PE, Parquet N, Brignier AC, et al. Serum hyperviscosity syndrome: Update 2024. Rev Med Interne. 2024;45(12):759-766. PMID 39117483. https://doi.org/10.1016/j.revmed.2024.07.008
Ito K, Kawasaki T, Hirano K, et al. Efficacy and safety of therapeutic procedure for Waldenström's macroglobulinemia with hyperviscosity syndrome. Ther Apher Dial. 2024;28(3):417-423. PMID 38069574. https://doi.org/10.1111/1744-9987.14094
Pessach I, Dimopoulos MA, Kastritis E. Managing complications secondary to Waldenström's macroglobulinemia. Expert Rev Hematol. 2021;14(7):621-632. PMID 34170207. https://doi.org/10.1080/17474086.2021.1947236
Medical disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have about a medical condition. Never disregard professional medical advice or delay seeking care because of something you have read here. If you think you may have a medical emergency, call your doctor or emergency services immediately.
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