What is a High Platelet Count?

A diagram of the composition of the blood, including platelets.
A high platelet count may be caused by an inflammatory disease like rheumatoid arthritis.
Routine blood tests can reveal a high platelet count and prompt doctors to do a thorough investigation.
People with essential thrombocytosis may suffer unexplained bruising.
Multiple blood samples may be necessary in order to get a clear analysis of a patient's blood count.
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  • Written By: D. Jeffress
  • Edited By: Bronwyn Harris
  • Last Modified Date: 29 July 2015
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Platelets are cells that are produced by bone marrow and released into the bloodstream. Their primary function is to release the hormones necessary to coagulate blood, preventing excessive blood loss from an internal or external injury. A normal platelet count for most humans is 150,000 to 450,000 per microliter of blood, and having a higher than average count can be indicative of serious health problems. A high platelet count can be caused by cancer, infections, anemia, and inflammatory diseases including rheumatoid arthritis and inflammatory bowel disease. A high platelet count can lead to excessive, dangerous blood clotting if left untreated.

The medical term for a high platelet count is thrombocytosis, a condition in which bone marrow cells produce too many platelets. Thrombocytosis can be either reactive or essential. Reactive thrombocytosis means that a high platelet count is a reaction to inflammation, infection, injury, anemia, or cancer, and essential thrombocytosis indicates that genetic conditions or hormone imbalances are causing irregular platelet formation. Individuals with the reactive form rarely experience symptoms, while people with essential thrombocytosis may suffer from blood clots in their extremities, nosebleeds, bloody stools, and unexplained bruising.


Individuals with essential thrombocytosis are at risk of developing dangerous blood clots that can lead to deep vein thrombosis, stroke, or heart attack. Reactive thrombocytosis may also result in excessive clotting, though the underlying causes are usually the most significant predictors of health problems. It is difficult to detect early warning signs of a high platelet count, and most people are unaware of their condition until they receive routine blood tests. A blood screening that suggests thrombocytosis will prompt a doctor to conduct a more thorough evaluation and determine the best means of treatment.

A physician might take more than one blood sample to get a clear analysis of a patient's platelet count. He or she generally asks the patient about medical and family history, including questions about past surgeries and diseases to determine if an underlying cause is leading to a high platelet count. Once the doctor has made a diagnosis of reactive or essential thrombocytosis, he or she will decide on the most appropriate treatment plan.

Treating reactive thrombocytosis usually involves curing the underlying cause. A patient may be given antibiotics or anti-inflammatory medicines to treat infections, or specialized drugs to combat anemia and other conditions that lead to a high platelet count. Doctors often suggest daily, low-dose aspirin for patients with essential thrombocytosis to help keep their blood from clotting. In severe cases, high-strength medications can be prescribed to suppress the production of platelets in bone marrow cells. Doctors usually suggest that patients with either type of thrombocytosis improve their daily diet and exercise routines, abstain from smoking, and schedule regular checkups to ensure they remain healthy.


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Discuss this Article

Post 19

My mom is 51 and she had a stroke a year ago. After that, she started taking aspirin and atrovastatin for one year. Recently her platelets started to increase. They were 630. Is it because of the medicine or some other cause? Now the doctor has asked to consult a hematologist. Is this serious?

Post 18

My platelet c ount is 4,60,000, and I understand that normal range is up to 4,50000. How do I reduce the platelet count and is there is any serious illness? I am perfectly in good health so far. Please reply.

Post 16

I first learned that I had thrombocytosis 25 years ago, when my platelet count was 1.2 million. 150,000 to 450,000 per microliter is normal. My doctor said that I probably had it for many years prior to discovery. I need to take Hydroxyuria capsules (3,000 mg/day) to bring down the platelets to 550,000. But, then my white blood cells also drop to 350,00 (380-108,000 is normal) and my red blood cells drop to 310,000 (400,000 to 620,000 is normal). So, I become susceptible to decease and anemic.

About 20 years ago, I decided to take only 1,000 mg/day of Hydroxyuria. My platelet count now stays at around 850,000. I am healthy and not anemic. My question: Does thrombocytosis really cause stokes, or is it just a theory? Are there actual medical/clinical studies that confirm it? What are the numbers - control group versus at risk group?

Post 15

What does this mean?: "Abnormal, your blood cell mass has increased significantly and your platelets, the part of the blood that is involved with clotting, has decreased significantly."

Post 14

My mom is 45 and she had a stroke. After that, she started taking aspirin. Recently her platelets started to increase. They were 625. Is it because of the medicine or some other cause? Now the doctor has asked to consult a hematologist. Is this serious?

Post 13

I was told that I have thrombocytosis. I went for a regular check up and was told my diagnoses over the phone with no real answer to what to expect from this. What can I do to lower my platelet count.

Post 12

My four year old son's blood tests showed he had elevated transaminases and platelets that were on the high end of high. He's having more tests in a month. What could be the cause of this? Should I be concerned?

Post 9

my mum was recently being treated for severe anemia. her iron level seems to be rising now but she has a high white blood and platelet count. What can this suggest?

Post 8

I had two operations with key hole in October and then had a blood clot and peritonitis and my platelet level is currently 1200. I am just taking aspirin just now and so long as you are active it generally sorts itself out, unless there is an underlying infection.

Post 7

I recently went to the doctor when I had a bad cold. I had the cold for about five weeks and I went to the doc and he ordered a blood test and gave antibiotics. Everything came back normal, except the platelet levels, which were 664. Can a bad infection cause your platelet levels to increase to this level?

I am 30 years old and have always had normal levels. I am nervous about this. They just retested today. I have not gotten the results yet. The first doc. I saw was not concerned, but the doc I saw today was. Please help with some knowledgeable advice. Thanks!

Post 6

Gracie - 497 and 524 are effectively the same level as the counting methods are not perfect - if you saw levels increase by hundreds then you might have concern but not by ~25!

Post 5

What concerns should I have when my blood platelets dropped? when I saw the Hematologist than they shot back up to 524 from 497 a week before?

Post 3

@stormysummer, there are generally no symptoms of a high platelet count. If there are symptoms they are generally as a result of blocked blood vessels. These symptoms could include headaches, tingling in hands a feet or cold finger tips. A blood test is the best way to determine if a person suffers from Thrombocytosis though, since those symptoms could be completely unrelated.

Post 2

Do people with a high platelet count show any symptoms?

Post 1

The problem with having too many platelets is that it can cause clots to form when you don’t need them. A high platelet count (thrombocytosis) can happen for many reasons. Infections are often accompanied by a high platelet count. That is more common in children than adults. An inflammatory disease known as Kawasaki’s disease, mainly affecting children, also is associated with a high platelet count. In adults, rheumatoid arthritis can be a contributing factor.

Blood loss from trauma can cause the bone marrow to produce more red blood cells and more platelets. If a large amount of tissue is damaged following an accident or surgery, the body’s natural defense mechanism is to increase the platelet count to ensure adequate clotting.

Some medications, such as steroids, can cause a temporary increase in platelet count. Also, spleen removal can cause an increase in platelets.

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