Can birth control cause thrombocytosis (elevated platelet count)?

Birth Control and Elevated Platelet Count

Birth control does not cause thrombocytosis (elevated platelet count). The available evidence addresses platelet activation and function with hormonal contraceptives, but does not demonstrate an increase in platelet numbers 1, 2.

Key Evidence on Platelets and Hormonal Contraception

Platelet Count Remains Unchanged

• A retrospective study of 95 women using combined oral contraceptives found no change in mean platelet volume (MPV) or platelet counts after six months of use 3
• The hematological monitoring showed stable platelet values between baseline and six-month follow-up in women using oral contraceptives 3

Platelet Activation vs. Platelet Count

The confusion likely stems from the fact that hormonal contraceptives affect platelet function rather than platelet numbers:

• Combined oral contraceptives containing 30 micrograms ethinylestradiol cause increased platelet activation (measured by ADP and arachidonic acid-induced aggregation) and elevated beta-thromboglobulin release 2
• Lower dose formulations (20 micrograms ethinylestradiol) show less platelet activation changes compared to higher dose pills 2
• These changes in platelet function contribute to the 3-5 fold increased relative risk of venous thromboembolism with combined hormonal contraceptives, though absolute risk remains low at 0.05% per year in healthy adolescents 4

Clinical Context: Thrombocytopenia Considerations

The guidelines address low platelet counts (thrombocytopenia), not elevated counts:

• Women with severe thrombocytopenia can use progestin-only pills and implants (Category 2), but DMPA requires caution (Category 3) due to unpredictable bleeding patterns 5
• The concern with thrombocytopenia is increased bleeding risk, not thrombosis 5

Practical Implications

If a patient develops elevated platelets while on birth control:

• The thrombocytosis is not caused by the contraceptive and requires investigation for other causes (reactive thrombocytosis from inflammation, infection, iron deficiency, malignancy, or primary myeloproliferative disorders) 5, 3
• The contraceptive choice should be guided by thrombotic risk assessment rather than platelet count alone 1, 4

For women with pre-existing thrombocytosis:

• Progestin-only methods (pills, implants, intrauterine devices) carry minimal to no thrombotic risk and are preferred 1, 4
• Combined hormonal contraceptives increase thrombotic risk through enhanced platelet activation and should be avoided if other thrombotic risk factors exist 2, 6