Platelets: what they are, what they tell you and what a low count means

Platelets are cell fragments that stop bleeding when a blood vessel is damaged. Their count is part of the full blood count, the most common blood test. When it is low, a virus, a medicine or a problem in the tube are often behind it.

Why we test them

Platelets are made in your bone marrow. When a blood vessel is damaged, they stick to the wound and form the first plug, which stops the bleeding.

They live about ten days, so your marrow keeps making new ones. Their count shows whether it makes enough, or whether your body is using up too many.

They matter when they are high too: that is often an indirect sign of inflammation or low iron.

What they tell you, and what they do not

A low count is called thrombocytopenia. When it is very low, bleeding takes longer to stop. But sometimes the number is wrong, because the platelets stuck together in the tube.

If they are high, your body is usually reacting to something else: inflammation, an infection or low iron.

Either way, the number alone does not tell you why.

That is why they are read together with other tests:

Normal platelet levels

The lab decides what is normal. It is usually 150 to 400 x10⁹/L, for women and men alike. Your own report may print slightly different limits.

Your report may call them platelets or PLT, and the unit is written in different ways: x10⁹/L, x10³/µL, thousands per microlitre. The number is the same. Some reports count per mm³ and print it in full: 150 thousand per mm³ is the same as 150 x10⁹/L.

In pregnancy they can drop a little, and they usually go back to where they were after the birth.

In the Rosa report you also see your optimal range, together with MPV and the rest of the blood count.

What your result means

Find the row for your result, in x10⁹/L. Which values are dangerous? Below 50, see a doctor the same day; above 400, talk to your doctor, who will usually repeat the test.

If your platelets are low or high

Low platelets: the causes

The first ones are the most common, especially if the rest of the blood count is normal.

Low platelets: the symptoms

Often none: above 50 they usually cause no problems, and they are found by chance on a blood count. When they are lower, you may notice:

If you also feel very tired, look pale or keep getting fevers, talk to your doctor soon: other blood count values may be low too.

Falsely low platelets: when the tube is to blame

The blood tube holds a substance that stops the blood from clotting. In some people, in contact with it, the platelets stick together in clumps, and the machine counts fewer than there are. It is called pseudothrombocytopenia.

In your body the platelets are normal, and on its own it is not a health problem. Among people sent to a specialist because platelets are their only low value, more than one in ten have only this.

The lab spots it under the microscope, where the clumps show, and counts again from another tube, tested straight away. Your report may carry a note such as platelet clumps. If it has happened to you before, tell the lab when you have your blood drawn.

How to raise your platelets

They come back up once the cause passes, and that usually takes some time. If faster treatment is needed, your doctor decides it. Where to start:

What can skew the result

Besides platelets clumping in the tube, a few things change the number for a while. It helps to know them before you read it.

When to worry

Talk to your doctor if:

With Rosa, platelets below 50 x10⁹/L are always flagged to a doctor urgently, and above 400 they are flagged, usually with a repeat test.

Frequently asked questions

Low platelets: when should I worry? Above 50 they usually cause no problems, but the cause still needs finding with your doctor. See a doctor the same day if they are below 50 or tiny red spots appear on your skin for no reason. If bleeding will not stop, you see blood in your vomit, black or bloody stools, or you get a sudden, severe headache, call 112 or go to the emergency department.

Platelets at 125: should I worry? Usually not, if you feel well and the rest of your blood count is normal. It is a little below the limit on many reports, and at this level there are generally no symptoms. Show your report to your doctor, who will often have it repeated to rule out a problem in the tube, and look for the cause.

What should I eat with low platelets? Food alone usually does not bring them back up: the cause matters. A varied diet with vegetables, legumes, fish and eggs gives you vitamin B12 and folate, which your body needs to make them. If you drink a lot, cutting down helps.

Can low platelets be a sign of cancer? Usually not: the most common causes are a problem in the tube, a virus, a medicine or an immune form. More rarely a bone marrow disease such as leukaemia is behind it, and then other blood count values are usually off too.

Does cortisone raise platelets? In some immune forms cortisone is one of the possible treatments, but a haematologist decides it. It is not something to take on your own to raise your platelets.

How often should they be checked? For people who feel well there is no fixed rule: Rosa measures them twice a year, with the blood count. If they are out of range, your doctor decides when to check again.

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