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Activated Clotting Time (Normalized Confirmatory, Plasma-based)

Published: August 9, 2026Updated: August 16, 2026

This test measures how long it takes for your blood to clot after activation, using plasma. It’s used to monitor anticoagulant therapy, such as heparin, and ensure safe dosing.

Quick summary

["Helps doctors check if blood-thinning medications are working properly or if adjustments are needed."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
75913-4
Short code
Normalized confirm dRVVT StaClot
Synonyms
Normalized confirm dRVVT StaClot
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
coag-drvvt-hexagonal-phase-phospholipid
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is This Test Measuring?

The test evaluates the time it takes for your blood plasma to form a clot after the addition of a specific activator. This helps assess the activity of clotting factors and anticoagulant medications.

Why Might You Need This Test?

Your healthcare provider may order this test if you’re on blood-thinning drugs (like heparin) to prevent blood clots, or if you have conditions that affect blood clotting, such as certain heart conditions or bleeding disorders.

How Is the Sample Collected?

A small amount of blood is drawn from a vein, typically in your arm. The blood is then processed into plasma for testing.

What Does the Result Mean?

Results are compared to a baseline or previous measurements to determine if your blood is clotting too quickly or too slowly, which could indicate whether your medication is effective or if changes are needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: This test is critical for patients on anticoagulant therapy to prevent excessive bleeding or clotting. Abnormal results may prompt dose adjustments or further evaluation of underlying clotting disorders.

Short name

ACT (Normalized Confirmatory)

Frequently asked questions

Why was I asked to take this test?
You may have been prescribed blood-thinning medication, such as heparin, or have a condition that affects blood clotting. This test helps ensure your medication is working safely and effectively.
What are the possible risks or side effects?
The most common risk is mild bruising or soreness at the needle insertion site. Rarely, blood clots or allergic reactions can occur, but these are usually managed promptly.
How soon will I get my results, and what should I do next?
Results are typically available within 24–48 hours. Follow up with your healthcare provider to discuss any findings and next steps, such as medication adjustments or further testing.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy