Lyme Disease Blood Test: What It Measures, Preparation, and Results

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A Lyme disease blood test is usually an antibody test. Instead of looking directly for the tick-borne bacterium, the test looks for immune proteins your body may make after exposure to Borrelia burgdorferi or related Lyme disease bacteria. That distinction matters: antibodies can take weeks to appear, and they can remain detectable long after an infection has been treated.

For most people, the recommended laboratory approach is a two-step blood testing process. The first test is typically an enzyme immunoassay, often called an EIA or ELISA. If that first step is negative, testing usually stops. If the first step is positive or equivocal, the lab performs a second test on the same blood sample. The Centers for Disease Control and Prevention (CDC) explains that the overall result is considered positive only when the testing algorithm meets the required criteria across both steps; CDC also notes that many laboratories now use a modified two-tier method in which both steps are EIAs rather than a Western blot as the second step. CDC: Clinical Testing and Diagnosis for Lyme Disease

What does a Lyme disease blood test measure?

A standard Lyme disease blood test measures antibodies, not live bacteria. Antibodies are immune system proteins that recognize parts of an infectious organism. In Lyme disease, the target is usually Borrelia burgdorferi, the main cause of Lyme disease in the United States.

Many reports include one or both of these antibody classes:

• IgM antibodies: often associated with early immune response. IgM can be useful only in a narrow early window and is more prone to false-positive interpretation if used later.
• IgG antibodies: typically develop later and are the more meaningful antibody class when symptoms have been present for more than several weeks.

The result does not tell you how many bacteria are in your body, whether a tick is still attached, whether symptoms are definitely caused by Lyme disease, or whether an infection has been cured. A positive result must be interpreted together with symptoms, physical findings, timing, and exposure risk.

When is a Lyme disease blood test useful?

Testing is most useful when the pre-test probability is reasonable: you have symptoms that fit Lyme disease and a credible chance of exposure to infected blacklegged ticks. Examples include a recent tick bite in an endemic area, an expanding rash compatible with erythema migrans, facial palsy, meningitis-like symptoms, certain heart rhythm problems, or swollen joints that could represent Lyme arthritis.

However, not every tick bite requires blood testing. In very early Lyme disease, especially when the classic expanding erythema migrans rash is present, clinicians may diagnose and treat based on the clinical picture because antibody tests can still be negative. The 2020 guidelines from the Infectious Diseases Society of America, American Academy of Neurology, and American College of Rheumatology recommend clinical diagnosis rather than laboratory testing for typical erythema migrans in an endemic area, while recommending antibody testing for several later or more complex presentations. IDSA/AAN/ACR 2020 Lyme Disease Guidelines

Testing is less helpful when symptoms are vague and exposure risk is low. Fatigue, headaches, muscle aches, and brain fog can occur with many conditions. If a Lyme test is ordered when the likelihood of Lyme disease is low, the chance that a positive result is misleading increases. That is why a careful exposure and symptom history is part of good test interpretation.

How two-tier Lyme disease testing works

Most recommended Lyme testing follows a two-step strategy designed to balance sensitivity and specificity. The first step is meant to screen for possible antibodies. The second step helps confirm whether the antibody pattern is specific enough to support Lyme disease.

Step	Common method	What happens next
Step 1	EIA, ELISA, or similar immunoassay	If negative, the report is usually interpreted as negative. If positive or equivocal, the lab reflexes to step 2.
Step 2: standard two-tier testing	IgM and/or IgG immunoblot, historically called Western blot	The final interpretation depends on the first-step result, the second-step band pattern, and symptom duration.
Step 2: modified two-tier testing	A second EIA using different antigens or design	If both steps meet the algorithm’s criteria, the final result may be reported as positive.

In 2019, CDC updated its recommendations to recognize FDA-cleared modified two-test algorithms as acceptable alternatives to standard two-tier testing when used according to the test instructions. CDC MMWR: Updated Recommendation for Serologic Diagnosis of Lyme Disease

You may see several names on a lab order or report: Lyme antibody screen, Lyme EIA, Lyme ELISA, Lyme total antibody, Lyme IgM, Lyme IgG, immunoblot, Western blot, or modified two-tier testing. These are not always interchangeable, so it is important to read the final interpretation rather than focusing only on one line item.

How to prepare for a Lyme disease blood test

Most Lyme disease blood tests require no special physical preparation. You usually do not need to fast, stop drinking water, or change normal activities. The sample is collected like many other blood tests: a phlebotomist cleans the skin, places a small needle into a vein, fills one or more tubes, removes the needle, and applies a bandage.

The most important preparation is informational. Before the blood draw, be ready to share:

• When symptoms started. The timing affects whether IgM is meaningful and whether an early negative result could be premature.
• Where you may have been exposed. Include travel, outdoor work, hiking, camping, yard work, pets, and time in wooded or grassy areas.
• Whether you saw a tick. If you did, estimate when it attached and when it was removed. Do not worry if you never noticed a tick; many people do not.
• Rash details. Note when it appeared, whether it expanded, its size, and whether photos are available.
• Antibiotic use. Early antibiotic treatment can reduce the chance of developing detectable antibodies.
• Immune system factors. Tell your clinician about immune-suppressing medicines, immune deficiencies, autoimmune disease, or conditions such as rheumatoid arthritis that may complicate interpretation.
• Pregnancy or breastfeeding. This does not usually change the blood draw but may affect clinical decision-making.

If you are ordering testing through a direct-to-consumer route, consider whether you will have a clinician available to interpret the results. Lyme serology can be confusing, and acting on an isolated IgM result, a single Western blot band, or a “past exposure” pattern without clinical context can lead to unnecessary treatment or missed alternative diagnoses.

How to interpret Lyme disease blood test results

The final interpretation is more important than any single number or band. Laboratories may use different wording, but common result categories include negative, equivocal, positive, IgM positive, IgG positive, or “antibodies detected.”

Result wording	What it may mean	What to discuss with your clinician
Negative	No laboratory evidence of Lyme antibodies under the test algorithm.	If symptoms began very recently, ask whether testing was done too early and whether repeat testing is appropriate.
Equivocal or indeterminate screen	The first test was not clearly negative or positive.	Confirm whether a second-tier test was performed and what the final two-tier interpretation says.
Positive two-tier result	Antibody pattern meets criteria for Lyme disease exposure or infection.	Review symptoms, exposure, timing, prior Lyme disease, and whether treatment is indicated now.
IgM positive only	May support recent infection if symptoms are within about 30 days; more likely misleading if illness has lasted longer.	Ask whether IgM should be considered based on symptom duration.
IgG positive	Can fit later infection, prior treated infection, or past exposure.	Discuss whether your current symptoms match active Lyme disease or another diagnosis.

What a negative result can mean

A negative result often means Lyme disease is unlikely, especially if symptoms have been present long enough for antibodies to develop and testing used a recommended two-tier method. But a negative test does not always rule out very early infection. CDC notes that antibody tests can be negative during the first weeks after infection because antibodies take time to develop. CDC: Testing and Diagnosis for Lyme Disease

If your symptoms started only a few days ago, your clinician may recommend observation, clinical diagnosis if a classic rash is present, treatment when appropriate, or repeat testing later. The right next step depends on the full clinical picture.

What a positive result can mean

A positive two-tier result supports exposure to Lyme disease bacteria at some point. It does not automatically prove that every current symptom is caused by active Lyme disease. Antibodies can remain elevated for months or years after infection, even after successful treatment. CDC specifically cautions that antibody titers cannot be used to determine cure. CDC: Clinical Testing and Diagnosis for Lyme Disease

This is especially important for people who had Lyme disease in the past. If you were treated years ago and now have a positive IgG result, the test may be showing immune memory rather than a new active infection. Your clinician may need to assess new exposure, objective findings, and other possible causes of symptoms.

Why IgM needs special caution

IgM is often misunderstood. It can be useful early, but it can also create false alarms. CDC advises that positive IgM results should be disregarded when a patient has been ill for more than 30 days. CDC: Clinical Testing and Diagnosis for Lyme Disease

In practical terms, an IgM-only positive result months into symptoms should not be treated as proof of active Lyme disease without careful clinical review. Ask your clinician: “How long have my symptoms been present, and should IgM be considered in my case?”

Accuracy, false positives, and false negatives

No Lyme blood test is perfect. Accuracy depends on the disease stage, the test method, whether the algorithm was followed, and the person being tested.

False negatives

A false negative means the test is negative even though a person has Lyme disease. This is most likely early, before antibodies have developed. Early antibiotic treatment may also make a person less likely to seroconvert, meaning they may not develop a clearly positive antibody pattern. CDC lists both early testing and early treatment as reasons antibody results can be negative or hard to interpret. CDC: Clinical Testing and Diagnosis for Lyme Disease

False positives

A false positive means the test suggests Lyme antibodies when Lyme disease is not the cause. CDC notes that cross-reactions may occur with conditions such as relapsing fever, syphilis, rheumatoid arthritis, and Epstein-Barr virus infection. CDC: Clinical Testing and Diagnosis for Lyme Disease

False positives are more consequential when testing is done in people with low exposure risk or symptoms that do not fit Lyme disease. In that situation, even a technically positive result may be less likely to represent the true explanation for symptoms.

Nonstandard tests

Be cautious with tests that are marketed as more definitive but are not part of recommended, validated diagnostic algorithms. The IDSA/AAN/ACR guideline warns against using several nonstandard methods for clinical diagnosis, including urine antigen tests, lymphocyte transformation tests, quantitative CD57 assays, and nonstandard serology interpretation, because they lack adequate independent validation for routine clinical use. IDSA/AAN/ACR 2020 Lyme Disease Guidelines

How much does a Lyme disease blood test cost?

The cost of a Lyme disease blood test depends on how it is ordered, whether insurance is used, which lab performs it, and whether the first test reflexes to a second-tier test. With insurance, your out-of-pocket cost may be a copay, deductible amount, coinsurance, or no charge depending on your plan and medical necessity rules. Without insurance, the consumer price can vary because some orders include only the initial screen while others include reflex confirmatory testing when indicated.

When comparing prices, look beyond the advertised test price. The effective total cost may include a clinician order or telehealth fee, lab draw fee, processing fee, reflex testing charges, and any follow-up visit needed to review results. If testing is ordered by your own clinician, ask whether the lab is in network and whether a positive or equivocal screen will trigger an additional billed test.

Cost factor	Why it matters
Initial screen versus reflex panel	A low listed price may not include the second-tier test if the screen is positive or equivocal.
Provider or ordering fee	Some direct-access options require a separate clinician authorization or service fee.
Collection location	Availability can differ by state, lab network, and whether a blood draw appointment is required.
Insurance network status	Using an out-of-network lab can raise out-of-pocket costs.
Follow-up care	Interpreting a complex result may require a visit with a clinician familiar with Lyme testing.

If you are paying cash, compare the total price for the full testing pathway, not just the first line item. If you have symptoms that could represent early or disseminated Lyme disease, do not let price shopping delay urgent medical care, especially if you have facial weakness, chest pain, fainting, severe headache, neck stiffness, pregnancy, or a swollen painful joint.

What to do after you get results

Your next step depends on the result, your symptoms, and the timing of possible exposure.

• If your result is negative and symptoms are very recent: ask whether the test may have been done before antibodies developed. Your clinician may recommend repeat testing, clinical monitoring, or treatment if the physical findings are characteristic.
• If your result is negative and symptoms have been present for weeks or months: ask what other diagnoses should be considered. Lyme disease is only one possible cause of fatigue, pain, neurologic symptoms, or joint complaints.
• If your result is positive: review whether the report reflects a complete two-tier algorithm. Ask whether the pattern suggests recent infection, past infection, or a result that needs clinical correlation.
• If only IgM is positive: confirm symptom duration. IgM-only results are not reliable evidence of active Lyme disease when symptoms have lasted more than 30 days.
• If you were treated before: remember that antibodies can remain positive. A repeat antibody test usually cannot distinguish old treated infection from a new episode.

Seek prompt medical care rather than waiting for routine lab turnaround if you develop symptoms that could reflect more serious Lyme disease complications, such as facial droop, severe headache with neck stiffness, fainting, shortness of breath, chest pain, palpitations, or a large swollen joint. Emergency symptoms should be evaluated urgently regardless of whether a Lyme test is pending.

FAQs about Lyme disease blood testing

Is a Lyme disease blood test the same as a tick test?

No. A Lyme blood test checks your blood for antibodies. A tick test checks a tick for organisms it may carry. A positive tick test does not prove transmission occurred, and a negative tick test does not rule out other exposures. Medical decisions are usually based on your symptoms, exposure risk, and recommended human testing when appropriate.

Do I need to fast before a Lyme disease blood test?

Usually no. Lyme antibody testing does not typically require fasting. If your clinician ordered other blood tests at the same time, follow any instructions for those tests.

How soon after a tick bite should I test?

Testing immediately after a tick bite is often not helpful because antibodies may not have developed yet. If you develop a classic expanding rash or concerning symptoms, contact a clinician. Depending on the situation, diagnosis may be clinical, or testing may be done later when antibodies are more likely to be detectable.

Can a Lyme blood test tell if I am cured?

No. Antibodies can remain detectable for months or years after infection. A positive result after treatment does not necessarily mean treatment failed, and falling antibody levels are not a reliable cure marker.

What is the difference between IgM and IgG?

IgM is an early antibody class that is only useful in a limited early window. IgG usually becomes more important later. If symptoms have lasted more than 30 days, IgM results should generally not be used as evidence of active Lyme disease without strong clinical justification.

Why did my report show bands?

Band results appear on immunoblot or Western blot-style reports. Each band represents antibody reactivity to a specific bacterial protein. Do not interpret one band by itself. The final result depends on the full band pattern and whether the overall two-tier algorithm is positive.

Can Lyme disease testing be positive from another condition?

Yes. Cross-reactions can occur, including with some infections and autoimmune conditions. That is one reason two-tier testing and clinical context are important.

Should I order a Lyme blood test on my own?

Direct-access testing may be convenient, but Lyme results can be difficult to interpret. If you order on your own, plan how you will review the result with a qualified clinician, especially if the result is positive, equivocal, IgM-only positive, or inconsistent with your symptoms.

 

Sources

• Centers for Disease Control and Prevention: Clinical Testing and Diagnosis for Lyme Disease
• Centers for Disease Control and Prevention: Testing and Diagnosis for Lyme Disease
• CDC MMWR: Updated CDC Recommendation for Serologic Diagnosis of Lyme Disease
• IDSA/AAN/ACR 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease
• CDC Emerging Infectious Diseases: Current Guidelines, Common Clinical Pitfalls, and Future Directions for Laboratory Diagnosis of Lyme Disease
• U.S. Food and Drug Administration: Performance Characteristics for In Vitro Diagnostic Devices Detecting Antibodies to Borrelia burgdorferi

Educational disclaimer: This article is for general education and is not a diagnosis or treatment plan. Lyme disease testing should be interpreted by a qualified healthcare professional who can consider your symptoms, exposure risk, exam findings, medical history, and local tick-borne disease patterns.