Borrelia burgdorferi IgG and IgM (Lyme disease)

Have fatigue, joint pain, facial palsy or other symptoms developed after time outdoors or a tick bite? Testing antibodies to Borrelia burgdorferi helps a doctor confirm or rule out Lyme disease. It is most useful once symptoms exist, rather than immediately after a bite.

Who the test is for

• people developing fever, fatigue, headache and muscle and joint pain after a tick bite or time outdoors;
• people with sudden paralysis of one side of the face;
• people with recurrent swelling of a knee or another large joint without a clear cause;
• people with pain, tingling or weakness along nerves when a doctor suspects nervous system involvement;
• people with an unexplained heart rhythm disturbance after time outdoors;
• forestry workers, hunters, hikers and others frequently outdoors, when they have these symptoms.

For severe headache with neck stiffness and fever, confusion, fainting or a very slow pulse, call emergency assistance immediately (194 or 112).

What the test reveals

Lyme disease is transmitted by ticks, in Croatia most often in the northwest and continental regions. Ticks are most active in spring and early summer, remaining present until early autumn. The first sign is often redness around the bite expanding over days (erythema migrans). It is recognised on examination and treated without a blood test because antibodies are often absent at that stage.

The test measures two antibody types:

• IgM appear first, several weeks after infection.
• IgG appear later and can persist for months to years, even after successful treatment.

Antibodies need time, so testing can be falsely negative in the first four to six weeks. A positive or borderline result is usually confirmed by an additional immunoblot, showing which bacterial components the antibodies target. A doctor can request this test.

The procedure and preparation

Blood is taken from a vein, taking a few minutes. No fasting or special preparation is needed. State when you noticed the bite or symptoms began and whether you have already taken antibiotics, because this affects interpretation.

What your result means

• IgM and IgG negative: no antibodies are present. If symptoms began recently, it may be too early, so a doctor may repeat testing after four to six weeks. With symptoms lasting months, negative IgG makes Lyme disease unlikely.
• IgM positive, IgG negative: early infection is possible, but IgM is often falsely positive. If symptoms have lasted more than approximately a month, positive IgM alone usually does not confirm disease.
• IgG positive: there has been contact with Borrelia, recently or years ago. This does not itself establish that current symptoms are caused by Borrelia.
• Borderline result: testing is usually repeated, and a doctor may also request immunoblot confirmation.

Thresholds are printed on the report. Antibodies alone are insufficient for diagnosis: a doctor interprets results alongside symptoms, examination and bite history.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels are available in the price list. Read more about antibodies to different pathogens on this page: Serology.

Frequently asked questions

Should I be tested immediately after a tick bite?

No. Testing immediately after a bite cannot show a new infection, and an asymptomatic bite is not a reason to test. Remove the tick promptly and monitor the bite site for about a month. See a doctor for spreading redness or other symptoms.

When after a bite is testing useful?

When symptoms suggesting Lyme disease appear, apart from typical redness diagnosed by examination. If an early test is negative but suspicion remains, a doctor repeats it after four to six weeks.

Can testing show whether treatment worked?

No. Antibodies persist for months to years even after successful treatment, so recovery is assessed through symptoms rather than repeat testing.

Can I have Lyme disease with a negative result?

Early on, yes, because antibodies have not yet developed. In later forms, such as arthritis, IgG is almost always positive, making disease unlikely with a negative result.