When to Get Tested for Lyme Disease After a Tick Bite
Do not get tested for Lyme disease after a tick bite if you have no symptoms. 1
Key Principle: Testing Asymptomatic Patients is Not Recommended
The IDSA/AAN/ACR guidelines strongly recommend against testing asymptomatic patients for exposure to B. burgdorferi following an Ixodes tick bite. 1 This is a strong recommendation based on moderate-quality evidence, meaning testing provides no clinical benefit and may lead to false positives that result in unnecessary treatment. 1
Instead of Testing: Use a "Wait-and-Watch" Approach
After a tick bite, the appropriate strategy depends on risk stratification rather than laboratory testing. 1
High-Risk Tick Bites (Consider Prophylaxis, Not Testing)
If ALL three criteria are met within 72 hours of tick removal, give prophylaxis instead of testing: 1, 2
- The tick is identified as an Ixodes species (deer tick/black-legged tick) 1
- The bite occurred in a highly endemic area for Lyme disease 1
- The tick was attached for ≥36 hours (can estimate by degree of engorgement) 1, 3
Treatment: Single dose of oral doxycycline 200 mg for adults or 4.4 mg/kg (maximum 200 mg) for children ≥8 years. 1, 3
Low-Risk or Equivocal-Risk Bites
If the tick bite cannot be classified with high certainty as high-risk, use a wait-and-watch approach rather than testing or prophylaxis. 1
When Testing IS Appropriate: Only After Symptoms Develop
Test When Erythema Migrans (Rash) Appears
If an expanding "bull's-eye" rash develops, diagnose clinically without laboratory testing. 1 The diagnosis of erythema migrans is clinical, not laboratory-based, and treatment should begin immediately with oral antibiotics (doxycycline, amoxicillin, or cefuroxime axetil for 10-14 days). 1
Test for Atypical Rashes
If a skin lesion is suggestive but atypical for erythema migrans, obtain antibody testing on an acute-phase serum sample, followed by a convalescent-phase sample 2-3 weeks later if the initial result is negative. 1 However, this is a weak recommendation based on low-quality evidence. 1
Monitor for 30 Days Post-Bite
Watch the bite area for 30 days for development of erythema migrans or systemic symptoms including fever, headache, fatigue, muscle pain, or joint pain. 3, 2, 4 If any of these develop, seek medical evaluation for clinical diagnosis and treatment. 4
Common Pitfalls to Avoid
Testing the tick itself is not recommended. The presence or absence of B. burgdorferi in a removed tick does not reliably predict clinical infection. 1
Early serologic testing is unreliable. Antibody responses take weeks to develop, so testing immediately after a tick bite will be negative even if infection occurred. 1
The 72-hour window for prophylaxis is critical. After 72 hours, prophylactic antibiotics are no longer indicated, and the strategy shifts to monitoring for symptoms. 1, 4
Doxycycline prophylaxis prevents Lyme disease but not necessarily other tick-borne diseases. 3, 2 Remain vigilant for symptoms of other tick-borne illnesses like Rocky Mountain spotted fever (petechial rash on wrists/ankles), ehrlichiosis, or anaplasmosis. 3, 5