Doctor's Assessment Included
Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
Factor V Leiden
Factor V Leiden testing identifies the most common genetic cause of increased clotting. For older adults, knowing your genetic status helps contextualise age-related thrombotic risk.
What It Measures
This test identifies the Factor V Leiden mutation (R506Q) through DNA analysis. Results indicate whether you are negative, heterozygous (one copy), or homozygous (two copies) for the mutation.
Why It Matters
Factor V Leiden is present in approximately 5% of Caucasian populations. Heterozygous carriers have a 3-8x increased thrombosis risk; homozygous carriers have up to 80x increased risk. Knowing your status informs decisions about contraception, pregnancy, surgery, and travel.
When to Test
Testing is recommended for unexplained venous thrombosis (especially under age 50), family history of Factor V Leiden or thrombosis, recurrent pregnancy loss, or before starting oestrogen-containing contraception with a relevant family history.
Symptoms
Low Levels
A negative result means you do not carry the Factor V Leiden mutation. Your thrombosis risk from this factor is at the population baseline level.
High Levels
Carrying the mutation does not cause symptoms directly. It increases the statistical risk of developing venous thrombosis, particularly when combined with other risk factors such as surgery, immobility, pregnancy, or oestrogen use.
Lifestyle Tips
If you carry Factor V Leiden, reduce modifiable thrombosis risk factors: maintain a healthy weight, stay active, avoid smoking, stay hydrated during travel, and discuss all hormonal medications with your healthcare provider.
Frequently Asked Questions
Will I definitely get a blood clot if I carry Factor V Leiden?
No. Most heterozygous carriers never experience a clot. The mutation increases risk but does not guarantee a thrombotic event.
Should my family be tested?
If you are a carrier, first-degree relatives may benefit from testing, especially before high-risk situations like surgery, pregnancy, or starting oestrogen therapy.
Can I use hormonal contraception with Factor V Leiden?
Oestrogen-containing contraception significantly increases thrombosis risk in carriers. Progestogen-only methods are generally considered safer. Discuss options with your healthcare provider.