From the Guidelines
The lab evaluation for this 72-year-old female with burning tongue sensation should include testing for vitamin B12, folate, iron studies (including ferritin), complete blood count (CBC), fasting blood glucose, and HbA1c. Given her clinical presentation of glossitis (smooth, glossy, erythematous tongue) and burning sensation, nutritional deficiencies are highly suspected. Vitamin B12 deficiency is particularly common in elderly patients and those taking metformin, which can interfere with B12 absorption over time 1. Iron deficiency anemia can present similarly and should be ruled out. Folate deficiency often coexists with B12 deficiency. While her diabetes is reportedly well-controlled, confirming glycemic control with HbA1c is important as poorly controlled diabetes can contribute to oral symptoms. The most recent guidelines from 2025 emphasize the importance of HbA1c testing for diabetes management, highlighting its advantages over fasting plasma glucose, including greater convenience and preanalytical stability 1. Thyroid function tests may also be considered as hypothyroidism can sometimes present with oral manifestations. These tests will help identify the underlying cause of her glossitis, which is likely related to a nutritional deficiency exacerbated by her age and medication use, particularly metformin. Key considerations in interpreting laboratory results include the potential for preanalytic variability and the importance of using certified assays, such as those certified by the National Glycohemoglobin Standardization Program (NGSP) for HbA1c testing 1.
From the Research
Laboratory Evaluation
The patient's symptoms of a burning sensation along her tongue, combined with her medical history and current medications, suggest the need for a comprehensive laboratory evaluation. The following tests should be considered:
- Vitamin B12 level: Given the patient's long-term use of metformin, a common medication for type 2 diabetes, there is an increased risk of vitamin B12 deficiency 2, 3.
- Folate level: As folate deficiency can also cause similar symptoms, testing for folate levels is recommended 4, 5.
- Iron level: Iron deficiency can also lead to symptoms such as weakness and shortness of breath, making it a relevant test in this case 4.
- Full blood count: This test can help identify any underlying anemia or other blood-related disorders 4.
- Other tests: Depending on the results of the initial tests, additional evaluations may be necessary to rule out other potential causes of the patient's symptoms.
Rationale for Testing
The patient's use of metformin increases her risk of vitamin B12 deficiency, which can cause a range of symptoms including neurological and hematological abnormalities 2, 3. The laboratory tests listed above can help identify any deficiencies or underlying conditions that may be contributing to the patient's symptoms. A prompt diagnosis and treatment can help alleviate symptoms and prevent long-term complications 6, 5.