Thin blood means having too few platelets, a part of the blood that helps clots form. Thin blood typically does not cause symptoms but can lead to excessive bleeding and bruising.

Blood contains four main components: plasma, red blood cells, white blood cells, and platelets. Platelets are small cells that clump together and help blood clot.

Thin blood occurs when a person has a low number of platelets. Doctors refer to the condition as thrombocytopenia.

The normal level of platelets in the blood is between 150,000–450,000 per milliliter (mL). If levels of platelets fall below 150,000/mL, it may indicate thin blood.

This article will look at the causes of thin blood, the symptoms, and what a person can do about it.

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The body creates platelets in bone marrow and stores an amount of them in the spleen.

A range of factors may cause a low platelet count, including the following:

Decreased platelet production

Viral infections, such as HIV, hepatitis C, mumps, rubella, or the Epstein-Barr virus, may cause platelet numbers to fall.

Bone marrow disorders, such as leukemia and lymphoma, can also affect how many platelets the body can produce.


Some people take blood-thinning medications to reduce their risk of heart attack and stroke. Two main types of medication thin the blood are anticoagulants and antiplatelet drugs.

These medications impair blood clot formation but can also decrease platelet levels. Examples include:

The spleen produces platelets, so problems with the spleen can cause thin blood. Conditions that affect the spleen include:

  • splenomegaly, or enlarged spleen
  • hypersplenism, which may cause platelets to get trapped in the spleen

Increased breakdown of platelets

Certain autoimmune conditions, such as systemic lupus erythematosus (SLE), can increase the rate of platelet destruction. If the body does not make new platelets fast enough, a person may have thin blood.

Chronic liver disease (CLD)

CLD lowers thrombopoietin levels, which is the hormone responsible for stimulating platelet production. Low thrombopoietin levels reduce the rate at which the body produces platelets.

Other factors

There are also some physiological variables that affect platelet count:

  • Aging: Platelet numbers may become lower as a person ages.
  • Genetics: Some people have low platelet counts due to genetic factors.
  • Pregnancy: Low platelet counts affect close to 10% of pregnant people at the time of birth.

Symptoms of thin blood include:

  • slow wound clotting
  • bleeding gums
  • nosebleeds
  • blood in the stools
  • heavy menstrual flow without clots

Occasionally, a person with thin blood may also be prone to sudden bruising, known as purpura, or pinprick hemorrhages on the skin, known as petechiae.

Some people may not experience any symptoms.

A doctor can diagnose thin blood by looking at platelet numbers in a complete blood count or CBC.

When talking with a doctor, it is essential for a person to tell them about any medications or supplements that might be causing thin blood. These include over-the-counter painkillers, such as aspirin.

Thin blood presents problems with clotting, wound healing, and bruising.

On the other hand, thick blood can increase the risk of blood clots and thrombosis, which can be life threatening.

Risk factors for thick blood include:

Polycythemia is a condition that causes blood to thicken due to high numbers of red blood cells.

Doctors can prescribe anticoagulant medications, such as heparin and warfarin, when blood is thick and a person has an increased risk of blood clots, stroke, or heart attack.

Treatment for thin blood will depend on the underlying cause. However, sometimes treating the underlying cause may not change the platelet count, and the blood will remain thin.

On occasions, doctors will prescribe corticosteroids to treat thin blood in conditions such as idiopathic thrombocytopenic purpura (ITP). In severe cases, they may recommend a platelet transfusion.

It is crucial to contact a doctor for a diagnosis if a person has symptoms that might indicate thin blood. A doctor can help determine the underlying cause and develop a personalized treatment plan.

They can also advise a person on how to take precautions and manage problems caused by thin blood, including excessive bleeding.

Below are some frequently asked questions about thing blood.

What happens when your blood is thin?

When a person’s blood has a low level of platelets, it will not clot as it should. This can lead to excessive bruising and heavy bleeding.

Can drinking water thin your blood?

Dehydration can cause blood to thicken and blood vessels to constrict. Maintaining adequate hydration levels helps keep blood at an optimum thickness and is essential for overall good health. It is possible to overhydrate by drinking too much water, although this is uncommon.

The medical term for thin blood is thrombocytopenia. This occurs when there are low levels of platelets in the blood. Platelets are small cells that clump together to form clots.

Having low platelet levels does not normally cause symptoms but can lead to excessive bleeding and easy bruising.

Viral infections, spleen disorders, medications, and other chronic conditions can all cause low platelet levels.

Treatment for thin blood will depend on its underlying cause.