From the Guidelines
To evaluate memory loss, laboratory tests including thyroid function tests, vitamin B12, homocysteine, complete blood count with differential, complete metabolic panel, erythrocyte sedimentation rate, and C-reactive protein are recommended, as they help identify reversible causes of memory loss. These tests should be part of a comprehensive diagnostic approach that also includes a thorough clinical evaluation, cognitive assessment, medical history, and possibly brain imaging studies like MRI. The choice of laboratory tests should be individualized to the patient’s medical risks and profile, as recommended by the Alzheimer's Association clinical practice guideline 1. According to the practical recommendations for timely diagnosis of symptomatic Alzheimer's disease, general labs including thyroid function tests, vitamin B12, homocysteine, complete blood count with differential, complete metabolic panel, erythrocyte sedimentation rate, and C-reactive protein should be requested 1. Additionally, structural brain imaging with MRI (or head CT if MRI is contraindicated) is also recommended as part of the diagnostic process 1. It is essential to note that while these tests are crucial, they should complement a thorough clinical evaluation, including cognitive assessment and medical history, to identify reversible causes of memory loss and provide appropriate treatment. The most recent and highest quality study, published in 2025, emphasizes the importance of a multi-tiered and individualized approach to laboratory testing in the evaluation of cognitive or behavioral symptoms 1. Therefore, a comprehensive metabolic panel, complete blood count, thyroid function tests, vitamin B12, and homocysteine levels, along with structural brain imaging, are essential components of the diagnostic process for memory loss.
From the Research
Laboratory Tests for Evaluating Memory Loss
The following laboratory tests are indicated for evaluating memory loss, also known as amnesia:
- Patient history
- Physical examination
- Mental status testing
- Functional assessment
- Laboratory tests, such as:
- Serum cholesterol
- Serum vitamin B12
- Folate
- Thyroid function tests
- Renal function tests
- Electrolyte tests (e.g. sodium)
- Blood glucose tests
- Complete blood count (CBC)
- Liver function tests
- Toxicology screens
- Infectious disease tests (e.g. syphilis, HIV)
Rationale for Laboratory Tests
These laboratory tests are used to identify potentially reversible causes of memory loss, such as:
- Metabolic disorders (e.g. diabetes, thyroid disease)
- Nutritional deficiencies (e.g. vitamin B12 deficiency)
- Infectious diseases (e.g. syphilis, HIV)
- Toxic exposures (e.g. heavy metals, medications)
- Structural brain lesions (e.g. tumors, strokes) As noted in the studies 2, 3, 4, 5, 6, a thorough assessment of a person presenting with memory impairment is mandatory, and laboratory tests can help identify underlying causes of memory loss.
Selection of Laboratory Tests
The selection of laboratory tests should be based on clinical indicators, such as:
- Patient history and physical examination findings
- Results of mental status testing and functional assessment
- Presence of symptoms or signs suggestive of a specific underlying cause (e.g. thyroid disease, vitamin B12 deficiency) As suggested by the study 2, a routine battery of laboratory investigations should be replaced with selected investigations based on clinical indicators only.
Diagnostic Impact of Laboratory Tests
The diagnostic impact of laboratory tests can be significant, as noted in the study 5, which found that additional testing led to a modification of the initial diagnosis in 17% of patients. However, the study also noted that the frequency of change was highest in patients with an initial non-Alzheimer's disease dementia diagnosis.