LabInformationLab tests, explained

Prothrombin Test in California

Prothrombin Test is a laboratory test you can order directly. The prothrombin test measures how long it takes your blood to clot. It is often ordered to check for bleeding disorders, monitor blood-thinning medications, or assess liver function. This page covers the prothrombin test for people in California, in Pacific, from what it measures to how to arrange a draw.

Sample type
blood
Category
Coagulation
Turnaround
1-3 business days
Price
$29
Referral
Not required

The prothrombin test measures how long it takes your blood to clot. It is often ordered to check for bleeding disorders, monitor blood-thinning medications, or assess liver function.

What it measures

  • Prothrombin Time (PT) — The time in seconds for a clot to form.
  • International Normalized Ratio (INR) — A standardized ratio that allows comparison across labs.
  • Prothrombin Activity — A percentage showing how well your clotting factors work.
  • Fibrinogen — A protein that helps form clots; sometimes measured with PT.

Who it is for

A doctor may order this test if you have unexplained bleeding or bruising, or if you take warfarin or another blood thinner. It is also used before surgery or to monitor liver disease.

Preparation

No fasting is needed for a prothrombin test. Tell your doctor about all medications, especially blood thinners, as they can affect results.

Results and what they mean

Results are reported as seconds for PT and as a number for INR, along with a reference range. Your clinician interprets these values based on your health and medications. This is general information, not medical advice; discuss your results with a healthcare professional.

Requesting the Prothrombin Test in California

Order online, choose a certified collection site in California, and review results through a secure portal. No referral is required, and orders are processed confidentially. Access across Pacific is uneven, so confirming a site ahead of time is worthwhile.

Frequently asked questions

Does a prothrombin test hurt?

It is a standard blood draw from a vein in your arm. You may feel a brief pinch or sting.

How long does it take to get results?

Typically 1 to 3 business days, though it may be faster in urgent situations.

Can I eat or drink before the test?

Yes, you can eat and drink normally unless your doctor gives other instructions.

What if my INR is too high or too low?

Your doctor will review your results and may adjust medication or order further tests. Do not change any medication without talking to your doctor.

Prothrombin Test by city in California

All testing in California →   Full Prothrombin Test guide →