Factor II Activity (Prothrombin)
Measures the activity of clotting factor II (prothrombin), a central component of the coagulation cascade.
Used to investigate abnormal clotting or bleeding. Alongside Factor V Leiden, part of a thrombophilia workup — relevant to anyone with elevated hematocrit or a clot history.
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Order directly through Marek Diagnostics — no doctor's visit needed, drawn at any Quest location in the US. Code CAMERON applies 10% off automatically.
Order this test — 10% off → Browse all 102 markers →What Factor II Activity (Prothrombin) is usually tested alongside
On its own, one marker is a data point. These panels include Factor II Activity (Prothrombin) plus the markers that make it interpretable — each names every test, why it is on the list, and loads the whole set into your cart in one click at 10% off.
includes this + 8 more markers — Family history of clots, stroke or early heart attack; on testosterone or oestrogen; long-haul travel; or a standard lipid panel that looked fine and you don't believe it.
Would you feel it? Symptoms Factor II Activity (Prothrombin) helps explain
People rarely search for a marker — they search for how they feel. These are the complaints where this marker is worth checking, and whether it is a first-line test or a follow-up once the obvious causes are ruled out.
Why your Factor II Activity (Prothrombin) might be wrong
Most abnormal results are interference, not disease. These are the things that measurably move this specific marker — check them before you change anything. Each one says whether the number is wrong and should be repeated, badly timed and should be redrawn, or real with a cause worth explaining.
Both reduce measured activity — that is what they are for. Testing on treatment measures the drug.
Interpret only alongside anticoagulant status.
Same blood-to-citrate ratio problem as every other clotting assay — an under-filled tube over-anticoagulates the sample and skews activity.
Repeat any short draw before acting on the result.
What Factor II Activity (Prothrombin) means in combination
A single marker tells you a little. Combinations tell you the story — these are the named patterns this marker takes part in, and what each one points at.
One copy raises clot risk modestly; two copies raise it far more. A report saying only 'positive' conflates two quite different situations. It also changes contraception advice substantially, and matters around surgery, pregnancy and long-haul travel.
Get the zygosity. Combined hormonal contraception carries markedly higher risk with this variant — that is a prescriber conversation, and it matters for siblings and children too.
Long endurance events reliably raise high-sensitivity troponin in healthy athletes with no cardiac damage, and kidney impairment raises the baseline. Heterophile antibodies and macrotroponin produce persistently raised values in people with entirely normal hearts.
Do not draw within a week of a long endurance event. A stable unexplained troponin is more likely an assay issue than disease — but that is a cardiologist's call. Chest pain or breathlessness is an emergency, not a lab order.
What to test next
Markers rarely answer alone. These are the ones that put Factor II Activity (Prothrombin) in context — each with its own full breakdown.
Frequently asked questions
70–130% of normal activity Ranges vary by laboratory and assay — always compare to the range printed on your own report.
Optimal ranges, root causes and the full correction protocol are available inside Coach Cam's Peptide Academy.
See the full breakdown inside the Academy.
See the full breakdown inside the Academy.
You can order Factor II Activity (Prothrombin) directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.