- 01A Lyme test reads your antibodies, so it has to be read against the calendar
The standard Lyme blood test detects the antibodies your body makes against Borrelia, and those antibodies take 2 to 6 weeks to appear and can last for years 4. The same test therefore misses most infections at the rash stage, finds nearly all late Lyme arthritis 4, and stays positive after a cure 5. A result only makes sense next to the date of the bite or the first symptom.
The standard Lyme disease test is a blood test for antibodies, the proteins your immune system makes against Borrelia, the spiral bacterium that causes Lyme disease. Antibodies take weeks to build and years to fade, so a Lyme antibody test can miss a new infection and still read positive long after a cured one. If you have a tick bite, a rash, or weeks of aches after time outdoors, read any Lyme result with the date of the bite or the first symptom written beside it.
What Lyme disease is
Lyme disease is an infection with Borrelia, a group of related spiral bacteria carried by blacklegged ticks (Ixodes species). North America and Europe have different Borrelia species, and the European ones lean more towards skin and nerve problems. That matters for testing, because an assay built around US strains can read some European infections less reliably 4.
Lyme disease is common where these ticks live. An estimated 476,000 people a year are diagnosed and treated for Lyme disease in the US, most of them in the Northeast and upper Midwest 7. In the UK and the rest of Europe, the risk sits mainly in woodland, heath and long grass. People catch Lyme disease from an infected tick, not from other people, and the US guideline treats a bite as high risk only when the tick has been attached for 36 hours or more, because Borrelia usually needs that long to cross into the skin 1.
Lyme disease symptoms by stage
Lyme disease moves through three loose stages if it goes untreated. The stage also predicts how well the antibody test performs, which is why the last column below matters as much as the symptoms 4.
| Stage | When it starts | Typical signs | What the antibody test does |
|---|---|---|---|
| Early localised | 3 to 30 days after the bite | Erythema migrans (an expanding red rash, often 5 cm or wider, sometimes with a clear centre); fever, aches, tiredness | Often negative: two-tier testing finds about 30 to 40% 4 |
| Early disseminated | Weeks to a few months | Several rashes, facial palsy (one side of the face droops), meningitis (inflamed lining around the brain), nerve pain, Lyme carditis with palpitations or fainting | Usually positive by now, as the longer-lasting antibodies (IgG) rise 4 |
| Late | Months to years without treatment | Lyme arthritis, usually one swollen knee; in Europe, acrodermatitis chronica atrophicans (thin, bluish skin on a hand or foot) | Close to 100% positive, with strong IgG 4 |
Most US patients develop the rash, but a minority never notice one, especially when it sits on the scalp, the back of a knee or the groin 4. Joint symptoms overlap with many other causes; the joint pain guide at /symptoms/joint-pain covers the wider list.
Do you need a Lyme test at all?
Two of the most common situations need no Lyme blood test. The UK guideline, which the NHS follows, puts the rash case plainly:
Diagnose and treat Lyme disease without laboratory testing in people with erythema migrans.NICE guideline NG95, Lyme disease, recommendation 1.2.7 2
- Tick bite with no symptoms: no test. Antibodies to that bite cannot have formed yet, and the US guideline advises against testing 1. Remove the tick, note the date and watch the skin for 30 days.
- Expanding rash after possible tick exposure: a clinician diagnoses and treats it on sight 12. A test taken at the rash stage misses most cases.
- Fever and aches, facial palsy, a swollen knee, palpitations or nerve symptoms weeks after possible exposure, without a typical rash: these are the situations where a Lyme blood test helps 12.
- Months of tiredness or pain with no tick exposure and no objective signs: the US guideline advises against Lyme testing on these symptoms alone, because a positive result is then more likely to be false 1. The fatigue guide at /symptoms/fatigue covers the usual causes.
How the Lyme blood test works
How a two-tier Lyme test reaches an answer
The CDC accepts either confirming route. The modified two-tier test (EIA followed by a second EIA) picks up slightly more early infections than the immunoblot route, with a similarly low rate of false positives 3. Your report will name the method; both are valid.
When to test: the Lyme antibody timeline
IgM antibodies, the immune system's first, short-lived response, usually appear around 2 weeks after infection. IgG antibodies, the slower and longer-lasting kind, take about 4 to 6 weeks to reach detectable levels and can stay for years 4. That timeline explains nearly every confusing Lyme result.
In a 2021 review in Clinical Microbiology Reviews, Branda and Steere put two-tier sensitivity at about 30 to 40% in early erythema migrans and close to 100% in Lyme arthritis 4. For timing, NICE says that if the first ELISA is negative, symptoms began within the last 12 weeks and Lyme disease is still suspected, the ELISA should be repeated 4 to 6 weeks after the first. If symptoms have lasted 12 weeks or more, the ELISA is negative and Lyme disease is still suspected, an immunoblot is done 2. Testing on the day of a bite tells you nothing about that bite.
Reading your Lyme test result
An immunoblot shows which Borrelia proteins your antibodies stick to. Each protein appears as a band named by its weight in kDa (kilodaltons), and the lab counts the bands. The IgM immunoblot counts as positive when 2 of 3 named bands are present (23 or 24, 39 and 41 kDa), and the IgG immunoblot when 5 of 10 bands are present 5.
| What the report says | What it usually means | Typical next step |
|---|---|---|
| Lyme antibody screen (EIA or ELISA) negative | No Borrelia antibodies found yet; early infection is still possible in the first weeks | If symptoms continue, the clinician may repeat it 4 to 6 weeks later 2 |
| Screen equivocal, or an index close to the cutoff | Borderline; handled the same as a positive screen | Goes on to the immunoblot or second EIA 5 |
| Screen positive, immunoblot negative | The screen most likely picked up cross-reacting antibodies | Usually reported as negative for Lyme 5; if symptoms began within the last few weeks, the clinician may retest later |
| IgM immunoblot positive, IgG negative | An early antibody response, meaningful only in the first 30 days of illness | After 30 days of symptoms, an IgM-only result is not counted as Lyme 5 |
| IgG immunoblot positive | Exposure to Borrelia at some point | Read with symptoms; an IgG result does not date the infection 4 |
| Still positive after treatment | Lyme antibodies persist for months to years | Not a sign the treatment failed; antibody tests cannot judge cure 5 |
The screen often comes with an index value, compared with a cutoff that each lab sets for itself, so read it against the reference range printed on the same report. What the H and L flags mean is covered at /learn/lab-report-flags-explained.
Free, no accountRead your blood testHave a Lyme antibody result with a CBC or liver panel on the same report? Read every line of it, free.Read my results
Why a Lyme test can be wrong
A false positive means the Lyme test reads positive without Lyme disease; a false negative means the Lyme test reads negative despite a real infection. Both have known causes 45.
| Causes of a false positive | Causes of a false negative |
|---|---|
| Recent Epstein-Barr virus (glandular fever) or another viral illness | Testing in the first 2 to 4 weeks, before antibodies form |
| Syphilis and other infections with spiral-shaped bacteria (spirochaetes) | Antibiotics started early in the illness |
| Lupus, rheumatoid arthritis and other autoimmune disease | Immune-suppressing medicines or conditions |
| An IgM immunoblot counted after the first 30 days of illness | European Borrelia species on an assay tuned to US strains |
| Labs reading blots with their own, looser band rules | Nerve infection, where spinal fluid tests outperform blood |
When a false positive is suspected, a clinician may look at the Epstein-Barr virus antibody panel (/biomarkers/ebv-antibody), rheumatoid factor (/biomarkers/rheumatoid-factor) or an antinuclear antibody test (/biomarkers/ana). How antibody tests for viruses are read is covered at /learn/viral-serology-explained, and lupus, which shares joint pain and tiredness with Lyme disease, at /conditions/lupus.
Other tests your doctor may use
- PCR on joint fluid: PCR detects Borrelia DNA, and joint fluid from a swollen knee is one of the few samples where Lyme PCR works well 4.
- PCR on blood: rarely positive, because Borrelia spends little time in the bloodstream 4.
- Spinal fluid antibody index: for suspected nerve infection (neuroborreliosis), comparing antibodies in spinal fluid with blood shows whether they are made inside the nervous system 4.
- Skin biopsy: occasionally used for an atypical rash or for acrodermatitis in Europe 4.
- ECG: a heart tracing checks for heart block (a delay in the heart's electrical signal) when palpitations, fainting or breathlessness suggest Lyme carditis 1.
Routine bloods taken for other reasons sometimes hint at Lyme disease. Mild rises in liver enzymes were found in about 40% of people with an early Lyme rash in one study, mostly ALT and GGT 6. None of these confirm Lyme disease, but together with a tick exposure they help a clinician decide whether to test. A raised AST is covered at /biomarkers/ast/high, and inflammation markers at /biomarkers/crp/high and /biomarkers/esr/high.
Routine markers that can shift in early Lyme disease
Lyme tests to be wary of
Some labs sell Lyme tests that have not been validated against confirmed cases. The IDSA guideline and the CDC advise against using these tests to diagnose Lyme disease 15:
- Urine antigen tests for Borrelia proteins
- CD57 lymphocyte counts
- Lymphocyte transformation tests (LTT), which measure T-cell reactions to Borrelia
- Immunoblots read with a lab's own band criteria instead of the published ones
A result from one of these tests can point people towards long, unneeded antibiotic courses or away from the real cause of their symptoms. If a report uses one of these methods, ask the clinician whether a standard two-tier test was also run. Which standard blood tests are worth asking for in general is covered at /learn/what-blood-tests-should-i-get.
Ticks often carry more than Lyme
Ticks can carry other infections too, some carried by the same blacklegged ticks and some by other species, and some show up on a routine blood count before any specific test is run. The US guideline suggests testing for anaplasmosis and babesiosis when Lyme symptoms come with high fever or abnormal blood counts 1.
| Infection | Clues on routine bloods | Usual test |
|---|---|---|
| Anaplasmosis | Low white cells, low platelets, raised ALT | PCR on blood or a blood smear 1 |
| Ehrlichiosis | Low white cells, low platelets, raised liver enzymes | PCR on blood |
| Babesiosis | Low platelets, anaemia, raised bilirubin | Blood smear or PCR 1 |
| Borrelia miyamotoi | Recurring fever, low white cells or platelets | PCR on blood |
| Powassan virus | Often normal; signs of brain inflammation | Antibody tests on blood or spinal fluid |
| Tick-borne encephalitis (Europe) | Often normal early; signs of brain inflammation | Antibody tests on blood or spinal fluid |
A low white cell count is explained at /biomarkers/wbc/low, with low lymphocytes and neutrophils at /biomarkers/lymphocytes-absolute/low and /biomarkers/neutrophils-absolute/low, and a low platelet count at /biomarkers/platelet-count/low. Anaemia is covered at /conditions/anemia and raised bilirubin at /biomarkers/total-bilirubin/high.
Blood count lines that can point to a co-infection
Can you test for Lyme at home?
Many home finger-prick Lyme kits run only an antibody screen, so check whether yours includes a confirming test. A home screen has the same timing limits as a lab screen: it can be negative in the first few weeks despite infection, and a positive result still needs a confirming immunoblot or second EIA before it means Lyme disease. As the guide at /learn/are-at-home-blood-tests-accurate puts it, "There is no single answer to whether a home blood test is accurate." A rash, facial droop or heart symptoms after a tick bite need a clinician the same day, not a kit.
Lyme disease treatment and what to expect
Lyme disease is treated with antibiotics chosen by a clinician. For an early rash, the IDSA guideline lists a 10-day course of doxycycline or a 14-day course of amoxicillin or cefuroxime as the usual options 1. Facial palsy, meningitis, carditis and Lyme arthritis can need longer courses or treatment through a drip, depending on the person and the stage 1. After a high-risk bite in an area where Lyme is common, the guideline also allows a single preventive dose of doxycycline within 72 hours of removing the tick, for people who meet its criteria 1. Whether any of these fits you is a decision for a prescriber.
Can Lyme disease be cured? In most cases, yes: most people recover fully after standard treatment. A minority have tiredness, pain or thinking problems that last 6 months or more, called post-treatment Lyme disease syndrome, and trials of prolonged antibiotics have not shown benefit for these symptoms 1. Lingering thinking problems are covered at /symptoms/brain-fog and persistent exhaustion at /conditions/chronic-fatigue-syndrome.
After a tick bite: remove, record, watch
- 1Remove the tick promptlyGrip the tick with fine-tipped tweezers as close to the skin as possible and pull upward with steady pressure. Avoid twisting, crushing, burning or smothering it 1.
- 2Clean the biteWash the bite and your hands with soap and water or an alcohol wipe.
- 3Record the date and placeWrite down when and where the bite happened and roughly how long the tick may have been attached. A clinician uses those details to judge risk 1.
- 4Watch for 30 daysCheck the bite and the rest of your skin for an expanding rash, and note any fever, aches, facial droop or joint swelling 1.
- 5Lower the next riskUse a skin repellent such as DEET or picaridin, treat clothing with permethrin, and check your body and your pets after time in long grass or woodland 1.
When to see a doctor straight away
- An expanding red rash after possible tick exposure: same-day or next-day appointment.
- One side of the face drooping, or new numbness, burning or shooting nerve pain (see /symptoms/tingling-hands-and-feet).
- A severe headache with a stiff neck or fever.
- Palpitations, fainting, chest pain or breathlessness (see /symptoms/heart-palpitations).
- A hot, swollen knee or other large joint.
- A high fever after a tick bite, with or without a rash.
Citations
- Lantos PM et al. 2020 IDSA/AAN/ACR Clinical Practice Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease. Clin Infect Dis 2021;72(1):e1-e48
- NICE guideline NG95: Lyme disease (2018)
- Mead P, Petersen J, Hinckley A. Updated CDC recommendation for serologic diagnosis of Lyme disease. MMWR 2019;68(32):703
- Branda JA, Steere AC. Laboratory diagnosis of Lyme borreliosis. Clin Microbiol Rev 2021;34(2):e00018-19
- CDC. Lyme disease: diagnosis and testing (clinical testing guidance)
- Horowitz HW et al. Liver function in early Lyme disease. Hepatology 1996;23(6):1412-7
- Kugeler KJ, Schwartz AM, Delorey MJ, Mead PS, Hinckley AF. Estimating the frequency of Lyme disease diagnoses, United States, 2010-2018. Emerg Infect Dis 2021;27(2):616-619
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
