Lyme Disease Western Blot
Confirmatory test for Lyme disease after positive screening.
Content last reviewed 2026-09-12 · Educational information — not medical advice
It is commonly considered when evaluating Lyme disease; people with Arthralgia, Bullseye Rash, Fatigue may have it ordered as part of their work-up.
What is the Lyme Disease Western Blot?
The Lyme Disease Western Blot uses clinical microbiology methods to look for evidence of infection or immunity.
How the Lyme Disease Western Blot works
Methods vary by pathogen: antibody serology detects your immune response (IgG/IgM), antigen tests find pathogen proteins, NAAT amplifies pathogen genetic material, cultures grow the organism, and microscopy inspects specimens directly.
Why healthcare providers order it
Ordered when exposure history, symptoms, travel, or screening protocols raise the question of a specific infection — and for immunity checks (titers) before school, work, pregnancy, or after vaccination.
Interpreting your results
Understanding infectious-disease results
- IgG positive: past infection or vaccination — usually immunity.
- IgM positive: suggests recent/active infection, though IgM can persist and false positives occur; confirmatory testing is standard.
- Antigen/NAAT positive: direct detection of the pathogen — active infection.
- Culture positive: organism grown and identified; sensitivity testing guides antibiotic choice.
- Negative: no detection, subject to window periods and specimen quality.
Reference intervals vary by laboratory, instrument, age, sex, and — for hormones — collection time. Always compare your value against the range printed on your own report, and review results with a qualified healthcare professional who knows your history. This guide is educational and does not diagnose.
Understanding your lab report
- Find the reference interval printed beside your value on the report — that pairing defines 'normal' for this lab run.
- Note the units. mmol/L vs mg/dL, ng/mL vs µg/L — numbers mean nothing across unit systems.
- Look at flags (H/L) but read the degree: barely-outside values behave differently than multiples of the limit.
- Trends outrank snapshots. A series of results tells your provider far more than any single draw.
Conditions that may involve Lyme Disease Western Blot
Symptoms that may lead to this test
Frequently asked questions
What does the Lyme Disease Western Blot measure?
It quantifies a specific biomarker or characteristic of the submitted sample, compared against a laboratory-defined reference interval.
Do I need to fast before the Lyme Disease Western Blot?
Fasting is not routinely required for this test; follow any instructions from your provider or laboratory.
How soon do Lyme Disease Western Blot results come back?
Most routine assays return within 1–3 business days; specialty methods can extend that to a week or more.
Can an abnormal Lyme Disease Western Blot result mean something serious?
Many of these infections are treatable; a positive result is interpreted with your symptoms, exposure history, and confirmatory testing.
Sources & data provenance
- Family-specific guidance compiled from standard clinical laboratory medicine references