Diagnosing hemophilia A

Learn about the specialty screening tests and evaluations required to diagnose hemophilia A.

Hemophilia A diagnosis

If a doctor suspects a patient may have hemophilia A, they will likely use blood tests (such as a complete blood test, coagulation tests, and measurement of factor levels) to help make a diagnosis. If blood clot formation is not within the normal range, then a clotting factor activity test is performed to confirm the diagnosis of hemophilia A or another blood-clotting factor deficiency.1

A healthcare provider may suspect hemophilia if2-4:

  • There is a family history of abnormal bleeding
  • A newborn has prolonged bleeding from heel sticks or following circumcision
  • A child has prolonged bleeding from the mouth after losing a tooth
  • A child has unexplained bruising when beginning to crawl or walk
  • Prolonged bleeding after injury or surgery occurs
Doctor discussing diagnosis with a patient.

Diagnosing hemophilia A: Step 1 (family history)2

A doctor will ask you if you’re experiencing any symptoms or if there’s any family history of hemophilia A. Those who live with mild or moderate hemophilia A might not be diagnosed until later in life after an injury or procedure that causes prolonged bleeding.

Diagnosing hemophilia A: Step 2 (tests)2,5

Next, your doctor will run a few blood-clotting tests, like the ones below:

Complete Blood Count

Measures hemoglobin and collects info about platelets and red and white blood cells.

Fibrinogen Test

Measures blood-clotting ability and is ordered with other blood-clotting tests or when a patient has an abnormal PT or APTT test results.

APTT (Activated Partial Thromboplastin Time) Test

Measures how long it takes for blood to clot and the clotting ability of a few factors like factor VIII levels.

Clotting factor tests

These tests tell your doctor the hemophilia type and severity.

PT (Prothrombin Time) Test

Also measures the time it takes for blood to clot for someone with hemophilia A.


Pharmacokinetics is the study of how the body absorbs, distributes, and processes drugs. Doctors can create personalized PK profiles that help them better understand how quickly a patient's body breaks down treatment, which is then used to tailor treatment to meet that patient's specific needs.

Diagnosing hemophilia A: Step 3 (genetic test)1

Your doctor may also run genetic testing to learn about:

Blood Tests

Any chance of developing hemophilia A inhibitors later down the line. Inhibitors are antibodies our immune systems make that can prevent treatment from working.

Genetic Tests

Gene mutations that can identify female hemophilia A carriers (this can be extremely helpful before and after a baby’s delivery).

Keep exploring

Doctor discussing treatment options with a patient during an appointment.

Treatment options for hemophilia A

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  1. National Organization for Rare Disorders. Hemophilia A. https://rarediseases.org/rare-diseases/hemophilia-a/. Accessed February 12, 2023.
  2. Centers for Disease Control and Prevention. Diagnosis of hemophilia. https://www.cdc.gov/ncbddd/hemophilia/diagnosis.html. Accessed February 12, 2023.
  3. Centers for Disease Control and Prevention. What is hemophilia? https://www.cdc.gov/ncbddd/hemophilia/facts.html. Accessed February 16, 2023.
  4. Srivastava A, Santagostino E, Dougall A, et al. WFH Guidelines for the Management of Hemophilia, 3rd edition. Haemophilia. 2020:26(suppl 6):1-158. https://doi.org/10.1111/hae.14046
  5. Grogan S, Preuss CV. Pharmacokinetics. 2022. https://www.ncbi.nlm.nih.gov/books/NBK557744/. Accessed February 12, 2023.