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Platelets (PLT)
The cell fragments that stop bleeding by forming clots. Too few raises bleeding risk, too many — the risk of clots.
Other names: Platelet count, thrombocyte countSection: Blood cells
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortPlatelets are the blood's first-response clotting cells. A typical adult count is 150,000–400,000 cells/mcL (150–400 × 10⁹/L). Below 150,000 cells/mcL (150 × 10⁹/L) is called thrombocytopenia, and below 50,000 cells/mcL (50 × 10⁹/L) everyday bleeding risk rises; at 400,000 cells/mcL (400 × 10⁹/L) or above the count is called thrombocytosis.
Reference ranges
Group
Reference range
Adults
150,000–400,000 cells/mcL (150–400 × 10⁹/L)
Thrombocytopenia
below 150,000 cells/mcL (150 × 10⁹/L)
Higher bleeding risk
below 50,000 cells/mcL (50 × 10⁹/L)
Thrombocytosis
400,000 cells/mcL (400 × 10⁹/L) or above
Common reference values from the MedlinePlus Medical Encyclopedia. Each laboratory sets its own interval — the range on the report applies.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
Platelets (thrombocytes) are small cell fragments released into the blood by the bone marrow. When a vessel is injured, they stick to the site, clump together, and form the plug that stops the bleeding — the first step before clotting proteins lock the plug in place.
Each platelet lives only about ten days, so the marrow replaces them continuously. A count reflects the balance between production, destruction, and sequestration in the spleen — and a shift in any of the three moves the number.
The count is a standard line of the complete blood count (CBC). It is ordered to find the cause of unusual bruising or bleeding, before surgery, and to monitor conditions and treatments — chemotherapy above all — that affect the marrow.
Some laboratories also report MPV, the mean platelet volume, next to the count: younger, larger platelets suggest the marrow is working hard to replace losses, while small ones point toward reduced production.
When it is high
Iron deficiencyA shortage of iron is one of the most common drivers of a reactive rise in platelets; the count usually settles as iron stores recover.
Recovery after infection, surgery, or traumaThe marrow temporarily overproduces platelets during recovery — a reactive, self-limiting pattern.
CancerSeveral cancers raise the count as part of the body's inflammatory response.
Bone marrow disordersMyeloproliferative neoplasms, including polycythemia vera, produce platelets without normal control and keep the count high.
Spleen removalThe spleen normally holds a share of platelets out of circulation; after splenectomy they stay in the blood and the count rises.
MedicinesCertain medicines raise the count — the provider reads the result against the current medicine list.
When it is low
Reduced marrow productionLeukemia, some anemias, viral infections, and marrow failure leave too few platelets being made.
Chemotherapy or radiationTreatment that targets dividing cells suppresses the marrow; counts are tracked closely through each cycle.
Autoimmune destructionImmune thrombocytopenia and similar conditions destroy platelets in the bloodstream faster than they are replaced.
MedicinesA long list of drugs — from heparin to some antibiotics — can lower the count; the medicine list is part of reading the result.
Spleen or liver diseaseAn enlarged spleen traps platelets; advanced liver disease reduces the hormone that stimulates their production.
PregnancyA mild drop late in pregnancy (gestational thrombocytopenia) is common and usually harmless, but it is still monitored.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Current or recent infectionChemotherapy and many other medicinesIron deficiencyPregnancySpleen conditionsRecent surgery or trauma
How to prepare
No special preparation is needed for a platelet count. It is part of the CBC, so any fasting requirement would come from other tests ordered for the same draw. Mentioning all current medicines to the provider matters — many of them move the count in either direction.
When a retest makes sense
A mildly low or high count is often confirmed with a repeat CBC, sometimes with a blood smear to rule out clumping in the tube (a known lab artifact). During chemotherapy or treatment of a platelet disorder the count is repeated as often as the treating provider's schedule requires.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; a hematologist if a blood disorder is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: PLTPlatelet countThrombocyte countPLT count
Units and conversion
Measured in: cells/mcL
cells/mcL=× 10⁹/L
cells/mcL ÷ 1,000 = value in × 10⁹/L. Example: 250,000 cells/mcL = 250 × 10⁹/L. Results are rounded to 2 decimal places.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
Easy bruising, pinpoint red spots on the skin, nosebleeds, bleeding gums, and longer bleeding from cuts. Below 50,000 cells/mcL (50 × 10⁹/L) even everyday activities can start bleeding, which is why that threshold gets attention.
Can the lab tube itself fake a low count?
Yes. Platelets sometimes clump in certain collection tubes (EDTA-dependent clumping), and the counter reads the clump as absent. A redraw into a different tube or a look at the smear resolves it.
Is a high count dangerous?
A reactive rise after infection or iron deficiency usually settles on its own. Very high counts can raise the risk of clots — or, paradoxically, of bleeding — so persistent elevation is investigated rather than watched.
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