Thick blood or hypercoagulability is a condition where the blood is thicker and stickier than usual. When a person has hypercoagulability, they are prone to excess blood clots. The condition is the result of an abnormality in the clotting process.

Among abnormalities that cause thick blood is an imbalance of proteins and cells responsible for blood clotting.

Thick blood can obstruct the movement of oxygen, hormones, and nutrients in the body, preventing them from reaching tissues and cells. This can cause low oxygen levels in the cells and lead to hormonal and nutritional deficiencies.

Fast facts on thick blood:

  • Mostly, there are few symptoms of thick blood until a significant blood clot forms.
  • Certain health conditions are linked to thick blood.
  • Treatment for thick blood depends on the condition causing it.
  • Doctors do not have a standard reference term for thick blood.

Some causes of thick blood are inherited, and others are developed, such as is the case with cancer.

Some of the medical conditions that cause the blood to thicken are listed below:

Certain cancers

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Thick blood may be caused by a number of conditions, including blood cancer.

Polycythemia vera (PV) is a blood cancer originating in the bone marrow or soft center of the bone where new blood cells develop. In the case of PV, the bone marrow makes too many red blood cells or too many white blood cells and platelets, causing blood to thicken.

Most people who develop PV do not have a family history of it, but in some cases, there can be more than one family member who has this type of blood cancer.

According to the Leukemia and Lymphoma Society, PV is more common amongst Jews of Eastern European heritage when compared to Asians and other Europeans. When all races and ethnicities are considered, the society estimates that PV affects 2.8 in 100,000 men and 1.3 in 100,000 women.

Waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a rare type of non-Hodgkin lymphoma where large amounts of the protein macroglobulin are produced. In some people with WM, when the cancerous B cells make too much of this protein, the blood can become extremely thick, leading to blood clots.

WM has only about 1,000 to 1,500 new diagnoses in the United States each year, according to the American Cancer Society.

SLE or lupus

Systemic lupus erythematosus, SLE, or lupus is an inflammatory disease that happens when the immune system attacks healthy tissues because it thinks they are diseased. According to the Lupus Foundation of America, 1.5 million Americans live with some form of Lupus, and the condition affects at least 5 million people worldwide.

Many factors contribute to blood thickening in lupus, but it is believed that autoimmune inflammation is the main culprit of procoagulant activity. Procoagulants are substances that stimulate proteins involved in the clotting process.

Factor V Leiden

Factor V Leiden is a genetic mutation of the coagulation cascade Factor V. This mutation increases a person's risk of blood clots, especially in the deep veins.

The additional clotting risk is because Factor V Leiden is resistant to being deactivated by a protein called activated protein C, which keeps normal Factor V activity controlled.

The result is excess Factor V activity, with blood clotting that exceeds normal levels, resulting in thickened blood.

Proteins C and S deficiencies

The hereditary types of these deficiencies are rare, but people with a deficiency of protein C or protein S are at a higher risk of blood clots for the rest of their lives, some having a blood clot at a young age.

Prothrombin Gene 20210A mutation

People with this genetic defect disorder have too much of the blood clotting protein called Factor II, also called prothrombin. Prothrombin is one of the factors that enable blood to clot correctly, but when there is too much prothrombin due to this mutation, a person will be at a higher risk of blood clot formation.

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Symptoms of thick blood may include lightheadedness, blurred vision, and headaches.

A hypercoagulability problem with a person's blood is often symptomless and will first show as a blood clot.

On some occasions, however, having a thick blood condition can cause symptoms in addition to blood clots. These symptoms depend on the cause of the condition and its location.

They may include but are not limited to:

  • blurred vision
  • lightheadedness
  • headaches
  • easy bruising
  • excessive menstrual bleeding or clotting
  • high blood pressure
  • lack of energy
  • shortness of breath
  • anemia when the blood is low in normal red blood cells

Blood clots of unknown origin, repeated blood clots, and recurrent pregnancy loss are reasons to be concerned about thick blood.

Anyone experiencing these symptoms or who has a family history of thick blood or blood clots should ask their doctor for testing. This will assess their risk for some of the medical conditions related to thick blood.

For conditions that affect blood clotting, doctors prescribe antiplatelet therapy or anticoagulation therapy.

  • Antiplatelet therapy: This involves medication that inhibits platelets, or the blood cells responsible for clotting, from forming clots. Aspirin is an example of antiplatelet therapy.
  • Anticoagulation therapy: This involves medicine to inhibit blood clotting at the level of the coagulation factors. Warfarin is an example of an anticoagulation drug.

Medications are only prescribed when doctors think there is an increased risk of blood clots, or a dangerous blood clot has already formed.

Since many people with thick blood may never experience blood clots, doctors are likely to recommend lifestyle changes to reduce the risk of clots and other complications. These changes include:

  • quitting tobacco smoking
  • losing weight, if necessary
  • staying active and engaging in daily physical activity
  • not sitting for long periods and moving legs and feet to keep blood flowing

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Thick blood may lead to deep vein thromboses (DVTs), which can be characterized by cramping and pain in the legs.

Thick blood disorders can create a lifetime of problems. These conditions can cause blood clots, including deep vein thromboses, otherwise called DVTs.

When a blood clot occurs in a deep vein, the result is pain and circulation problems around the area where the blood clot has formed. DVTs commonly form in the big veins deep in the lower legs but can occur elsewhere in the body, such as the thighs, arms, abdomen, or pelvis.

Symptoms of DVTs include:

  • swelling, redness, and warmth where the DVT occurred
  • gradual onset of pain
  • leg pain when bending the foot or stretching the leg
  • leg cramps in the calf
  • skin discoloration that is blue or white elsewhere in the body

A pulmonary artery embolism (PE) results when part of the DVT detaches or embolizes from its origination point and makes its way back to the heart and lungs. If this broken-off piece of clot makes it way to the heart and lungs and accumulates, it can prevent sufficient blood flow and interfere with gas exchange in the lungs.

Symptoms of a PE include:

  • shortness of breath and rapid breathing
  • rapid heartbeat
  • pain with deep breaths
  • blood when coughing
  • chest pain

Other possible and frequently serious complications of blood clots are:

  • Stroke if a blood clot moves to the brain and blocks an artery that sends oxygenated blood to the brain.
  • Heart attack resulting from a blood clot in a coronary artery.
  • Acute kidney injury, resulting from a blockage or blood clot of one or both of the renal veins that move blood away from the kidneys.

Thick blood on its own does not cause health problems, but certain medical conditions that cause blood to become thick can severely affect a person's life.

People who have thick blood are at greater risk of blood clots in the arteries and veins. Anyone who thinks they are experiencing a blood clot should seek medical attention immediately.

Anyone who has a family history of thick blood or blood clotting disorders should speak to their doctor about possible risks and complications.

Medications and lifestyle changes can help many people who have thick blood disorders and lower their risk of blood clots and other potential problems.