Diphtheria Antibody Test
Below is a plain-language overview of the diphtheria antibody test. The diphtheria antibody test measures the level of antibodies your immune system has made against diphtheria, a rare but serious bacterial infection. It is usually ordered to check whether a person has protective immunity after vaccination or to help evaluate a possible exposure.
- Sample type
- blood
- Category
- General Wellness
- Turnaround
- 1-3 business days
- Price
- $129
- Referral
- Not required
The diphtheria antibody test measures the level of antibodies your immune system has made against diphtheria, a rare but serious bacterial infection. It is usually ordered to check whether a person has protective immunity after vaccination or to help evaluate a possible exposure.
What it measures
- Diphtheria antitoxin antibodies — The main marker; shows how much protection you likely have against the toxin made by diphtheria bacteria.
- IgG antibody level — The type of antibody most often measured to reflect longer-term immunity.
- Protective threshold — A reference level used to judge whether immunity is likely adequate; exact cutoffs vary by lab.
Who it is for
A clinician may order this test for people with unclear vaccination records, those who work or travel in higher-risk settings, or patients being evaluated after a possible exposure. It is not a routine screening test for most adults.
Preparation
No fasting or special preparation is needed. A blood sample is drawn, usually from a vein in your arm, and you can eat and drink normally beforehand.
Results and what they mean
Results are reported as a numeric antibody level, often with a note about whether it is above or below a protective threshold. Your clinician interprets the number along with your vaccination history and symptoms. This is general information only and is not medical advice; discuss your results with a qualified healthcare professional.
How to order this test
- Choose the test and place a confidential order online.
- Select a certified collection site and pick a time that suits you.
- Have your specimen collected — most draws take only a few minutes.
- Review results in a secure portal, typically within 1–3 days.
Preparation, hours, and pricing vary by site; confirm details directly with the lab before your visit.
Availability by state
Direct-access online ordering for the diphtheria antibody test is available in most states. It is currently unavailable in 6 states:
Everywhere else you can order confidentially and collect your sample at a certified site. Browse by state →
Frequently asked questions
Do I need this test if I was vaccinated as a child?
Not usually. Most people who completed childhood vaccination have protection, and the test is mainly used when immunity is uncertain.
What does a low result mean?
A low level may suggest reduced protection, but your clinician will consider your history before recommending any next step.
Can I get this test without a doctor's order?
Some labs offer it directly, but a clinician should interpret the result in the context of your health.
How long does it take?
Results are typically available in 1 to 3 business days.