Laboratory Workup for Burning Tongue
Order a comprehensive metabolic panel, complete blood count with differential, hemoglobin A1c, vitamin B12, folate, iron studies (ferritin, serum iron, TIBC), thyroid function tests (TSH, free T4), vitamin D 25-OH, and zinc levels to exclude secondary causes of burning mouth syndrome before diagnosing primary burning mouth syndrome. 1, 2, 3
Essential Laboratory Tests
Hematologic Studies
- Complete blood count with differential to identify anemia, which commonly causes oral burning symptoms 1, 2
- Vitamin B12 levels as deficiency is a well-established cause of secondary burning mouth syndrome 1, 2, 4
- Folate levels to exclude nutritional deficiency contributing to oral burning 2, 4
- Iron studies (ferritin, serum iron, TIBC) as iron deficiency anemia frequently presents with burning tongue 1, 2
Metabolic and Endocrine Studies
- Hemoglobin A1c to screen for diabetes mellitus, which can manifest as burning tongue and taste alterations, particularly in undiagnosed diabetics with xerostomia 3, 4
- Comprehensive metabolic panel including glucose, electrolytes, and liver function tests to identify systemic abnormalities 2, 4
- Thyroid function tests (TSH, free T4) as thyroid disorders, particularly hyperthyroidism, can cause tongue erythema and burning 2
Vitamin and Mineral Studies
- Vitamin D 25-OH levels as deficiency is associated with burning tongue symptoms, particularly in diabetic patients with xerostomia 2, 3
- Zinc levels to exclude mineral deficiency as a secondary cause 2, 4
Additional Diagnostic Considerations
Immunologic Testing (When Indicated)
- Antinuclear antibodies and autoimmune markers if Sjögren's syndrome or other autoimmune diseases are suspected based on clinical presentation with dry mouth 2
- Elevated IgE levels may be present but are nonspecific findings in many conditions related to secondary eosinophilia and should not be routinely ordered unless specific allergic or parasitic conditions are suspected 1
Microbiologic Studies
- Oral swab with KOH preparation to exclude oral candidiasis, which must be ruled out before diagnosing primary burning mouth syndrome 2, 5
Clinical Context and Pitfalls
The diagnosis of primary burning mouth syndrome is one of exclusion and should only be established after all secondary causes have been ruled out through comprehensive laboratory evaluation 2, 4, 5. Multiple concurrent causes may be present in more than one-third of patients, making thorough laboratory screening essential. 4
A common pitfall is diagnosing primary BMS without adequate laboratory workup, as conditions like undiagnosed diabetes and vitamin D deficiency can present with burning tongue and taste alterations that resolve with treatment of the underlying condition 3. Another critical error is failing to recognize medication-induced burning mouth syndrome, particularly from ACE inhibitors and other antihypertensive or psychotropic medications 2, 6.
The combination of burning tongue with xerostomia should prompt immediate testing for diabetes and vitamin D deficiency, as these conditions frequently coexist and cause oral burning symptoms. 3