Also called: AT test, AT3, Antithrombin III test
Report
{context.blood_test.parameters} Parameters
What it checks
Report delivery
Test for
Age group
Commonly advised for
The Anti-Thrombin III test measures the level of antithrombin, a natural protein that helps regulate blood clotting by preventing excessive clot formation. Deficiency of antithrombin increases the risk of abnormal blood clots in veins and arteries.
This test is crucial in evaluating inherited or acquired clotting disorders, especially in patients with unexplained or recurrent thrombosis.
You may be advised this test to:
Evaluate recurrent or unexplained blood clots
Investigate thrombosis occurring at a young age
Assess pregnancy-related clotting complications
Screen for inherited clotting disorders
Evaluate family history of thrombosis
Antithrombin is a natural anticoagulant protein produced by the liver. It works by inactivating several clotting factors, preventing excessive clot formation. When antithrombin levels are low, the balance shifts toward clot formation, significantly increasing thrombosis risk. This test helps identify both inherited deficiencies (present from birth) and acquired deficiencies (developing due to other conditions).
Recurrent deep vein thrombosis (DVT)
Pulmonary embolism
Blood clots at unusual sites
Thrombosis at a young age (under 50)
Pregnancy-related clotting events
Family history of clotting disorders
Unexplained clot formation
Early detection of antithrombin deficiency helps prevent life-threatening clot formation and allows timely initiation of anticoagulant therapy. It also helps guide treatment decisions and family screening.
Inform your doctor about all medications, especially anticoagulants
Testing is ideally done when not on blood thinners, as they can affect results
No fasting is typically required
Discuss timing with your doctor if you're pregnant or recently had surgery
A blood sample is drawn from a vein in your arm and sent to the laboratory for analysis using specialized immunoassay or functional activity testing methods.
Results are typically available within a few days. If levels are low, your doctor may recommend repeat testing to confirm the diagnosis and rule out temporary causes.
Immediately if you experience symptoms of blood clots such as leg pain and swelling, chest pain, shortness of breath, or if your test results show low antithrombin levels.
Minimal risk related to blood draw only, including slight bruising or discomfort at the puncture site.
Stay active and avoid prolonged immobility
Maintain adequate hydration
Follow prescribed anticoagulant therapy if recommended
Inform healthcare providers about your condition before surgery
Wear compression stockings during long travel if advised
Avoid smoking, which increases clot risk
The test measures the concentration and functional activity of antithrombin III, a key anticoagulant protein that regulates blood clot formation.
Normal levels (80–120%): Antithrombin deficiency unlikely
Low levels (<80%): Increased risk of abnormal blood clots; may indicate inherited or acquired deficiency
Borderline levels: May require repeat testing for confirmation
Seek specialist care (hematologist) for further evaluation, confirmatory testing, family screening, and discussion of long-term anticoagulation therapy if needed.
Current use of anticoagulants (heparin, warfarin)
Acute thrombosis or recent clot formation
Liver disease
Pregnancy
Recent surgery or trauma
Certain medications
Timing of sample collection
Is antithrombin deficiency common?
No, antithrombin deficiency is rare, occurring in approximately 1 in 2,000 to 5,000 people, though it accounts for a significant proportion of inherited clotting disorders in younger patients with unexplained thrombosis.
Is it inherited?
Yes, antithrombin deficiency is often inherited in an autosomal dominant pattern, meaning a child has a 50% chance of inheriting the condition if one parent carries the deficiency; however, acquired deficiency can also occur.
Can pregnancy affect levels?
Yes, pregnancy can lower antithrombin levels temporarily due to increased consumption, hemodilution, and hormonal changes, which increases clotting risk; testing may need careful interpretation during pregnancy and postpartum periods.
Is treatment lifelong?
Sometimes, treatment duration depends on whether the deficiency is inherited or acquired, and whether clots have occurred; those with inherited deficiency and recurrent clots typically require lifelong anticoagulation therapy.
Is repeat testing required?
Yes, repeat testing is usually required to confirm the diagnosis, especially if initial levels are borderline or if testing was done during acute illness, anticoagulant use, or pregnancy when results may be temporarily affected.
Antithrombin III is a natural protein that stops your blood from clotting too much. This test is advised if:
Tapadia Diagnostic Centre in Karimnagar offers NABL-accredited Antithrombin III test from a Blood sample(s). AT test, AT3, Antithrombin III test is also prescribed for Chest pain, leg swelling, breathing trouble. Established in 1989, this doctor-led diagnostic centre ensures high accuracy. Home sample collection and walk-in facility available at our Karimnagar center. Pay at the centre with no advance payment. Book online or visit us.
Antithrombin III in Karimnagar
Rated 4.6 on Google
From 6,477 patient reviews across our Hyderabad centres.
Every report, kept for you
Past reports stay in your account and can be downloaded again.
NABL accredited
Every result reviewed by a qualified pathologist before it reaches you.
Four decades of practice
A family-run diagnostic centre, trusted by doctors and households since 1989


Antithrombin III in Vijayawada
Antithrombin III in Visakhapatnam
Antithrombin III in Ahmedabad
Antithrombin III in Bengaluru
Antithrombin III in Mumbai
Antithrombin III in Secunderabad
Antithrombin III in Karimnagar
Antithrombin III in Hyderabad
Antithrombin III in Warangal
Antithrombin III in Chhatrapati Sambhajinagar (Aurangabad)
Master Health Checkup (Blood) in Karimnagar
HIV 1 & 2 Antibodies, Serum-Elisa Method in Karimnagar
Dengue IgG, IgM Antibodies + NS1 Antigen-Rapid, Serum in Karimnagar
Lipoprotein A (Lp A), Serum in Karimnagar
Erythrocyte Sedimentation Rate (ESR) in Karimnagar
Thyroxine Total (T4), Serum in Karimnagar
Triiodothyronine Total (T3), Serum in Karimnagar
CA 19.9 (Pancreatic Cancer Marker), Serum in Karimnagar
NIPT with Microdeletions in Karimnagar
NIPT Basic in Karimnagar
Complete Blood Picture (CBP) in Karimnagar
Serum Phosphorus Test in Karimnagar
TIBC in Karimnagar
Urology Profile in Karimnagar
Beta HCG Free, Serum (Pregnancy Test) in Karimnagar
Viral Screening in Karimnagar
AFP Test in Karimnagar
Microalbuminuria test in Karimnagar
Diabetes Testing (FBS + PLBS) in Karimnagar
Antithrombin III in Karimnagar
D-dimer test in Karimnagar
Creatine Kinase (CK) Test in Karimnagar
AST Test in Karimnagar
Cardiac Markers in Karimnagar
Pap Smear - LBC in Karimnagar
DVT Profile in Karimnagar
Bleeding Time and Clotting Time (BT & CT) in Karimnagar
Estradiol Test in Karimnagar
hs-CRP Test in Karimnagar
Alkaline Phosphatase (ALP) Test in Karimnagar
Fertility Profile in Karimnagar
Albumin blood test in Karimnagar
Troponin T in Karimnagar
Infertility Profile Extended in Karimnagar
Electrolyte Panel in Karimnagar
Anticardiolipin Antibodies (IgG) in Karimnagar
PSA Test in Karimnagar
FSH Test in Karimnagar
STD Panel in Karimnagar
PCOS Profile in Karimnagar
Serum Iron Test in Karimnagar
Cardiac Profile-III in Karimnagar
Plasma Fibrinogen Test in Karimnagar
HBsAg Test in Karimnagar
Cardiac Biomarker Test in Karimnagar
Herpes Simplex Virus (HSV) Types 1 and 2 Antibody Test in Karimnagar
Antenatal Profile in Karimnagar
Activated Partial Thromboplastin Time in Karimnagar
Lipid Panel in Karimnagar
Fine Needle Aspiration Cytology in Karimnagar
CRP test in Karimnagar
Joint Pain / SLE / Collagen Profile-I in Karimnagar
PAPP-A Test in Karimnagar
Insulin Test in Karimnagar
Triple Screen Test in Karimnagar
Anti-HCV Test in Karimnagar
Basic Metabolic Panel (BMP) in Karimnagar
Very low-density lipoprotein (VLDL) test in Karimnagar
Free Testosterone in Karimnagar
Triglycerides Test in Karimnagar
Quad Screen in Karimnagar
Folic Acid in Karimnagar
Urinalysis in Karimnagar
CEA Test in Karimnagar
Ferritin Test in Karimnagar
Transferrin Saturation% in Karimnagar
Protein C Antigen in Karimnagar
Alpha Feto Protein (AFP) - Fluid in Karimnagar
CPK (MB) Test in Karimnagar
Lupus Anticoagulant Testing in Karimnagar
Reticulocyte Count in Karimnagar
Infertility Profile-Basic in Karimnagar
Beta hCG Test in Karimnagar
DIABETIC PROFILE in Karimnagar
LH Test in Karimnagar
Anti-Müllerian Hormone (AMH) Test in Karimnagar
Bile Salts and Bile Pigments, Urine in Karimnagar
HbA1c in Karimnagar
Vitamin D (1,25-Dihydroxyvitamin D) in Karimnagar
Liver Function Test (LFT) in Karimnagar
Anemia Profile Basic in Karimnagar
Rheumatoid Factor in Karimnagar
Widal Test in Karimnagar
Bilirubin blood test in Karimnagar
Inhibin A, Tumor Marker, Serum in Karimnagar
Thyroid Function Tests in Karimnagar
eGFR in Karimnagar
Menopause Profile in Karimnagar
EXTENDED DIABETIC PROFILE in Karimnagar
LDH Test in Karimnagar
Total Cholesterol Test in Karimnagar
Random Blood Sugar Test in Karimnagar
Total Protein Test in Karimnagar
RPR test in Karimnagar
Anti-dsDNA Test in Karimnagar
HDL Cholesterol in Karimnagar
Blood Type Test in Karimnagar
ASO Titre in Karimnagar
Blood Urea(Serum) Test in Karimnagar
Postprandial Blood Sugar Test in Karimnagar
Back Pain Profile in Karimnagar
ANA test in Karimnagar
Serum Creatinine Test in Karimnagar
PT/INR Test in Karimnagar
Fasting Blood Sugar Test in Karimnagar
Extended Anemia Profile III Executive in Karimnagar
Kidney Function Test (Renal Profile) in Karimnagar
Serum Magnesium Test in Karimnagar
Well-woman exam in Karimnagar
LDL cholesterol test in Karimnagar
Prolactin Test in Karimnagar
Malaria Blood Smear in Karimnagar
Liver Function Test (+GGT) in Karimnagar
TPHA Test in Karimnagar
Hepatitis B Surface Antigen (HBsAg) Test in Karimnagar
Antenatal Profile 2 in Karimnagar
TSH Test in Karimnagar
Cardiac Catheterization in Karimnagar
Cardiolipin Antibody (IgM) in Karimnagar
Master Health Checkup (BL+RADIO) in Karimnagar
Calcium Profile in Karimnagar
Coagulation Profile in Karimnagar
Uric Acid Test in Karimnagar
Vitamin D (25 - Hydroxy Vitamin D, Serum) in Karimnagar
Globulin Test in Karimnagar
Fever Profile Test in Karimnagar
Connective Tissue Disease Profile in Karimnagar
Calcium Blood Test in Karimnagar
IHC in Karimnagar
Estriol Unconjugated (E3) Test in Karimnagar
Blood Typing in Karimnagar
Vitamin B12 Test in Karimnagar
Serum Cortisol in Karimnagar
Double Marker Test in Karimnagar
Pap Smear, Conventional in Karimnagar
Protein S Activity in Karimnagar
Non-Invasive Prenatal Testing (NIPT) in Karimnagar
whole exome sequencing in Karimnagar
Newborn Screening (NBS) in Karimnagar
Apolipoprotein A1 (Apo A1), Serum in Karimnagar
Apolipoprotein B (Apo B), Serum in Karimnagar
Renal Function Test (RFT) in Karimnagar