Routine Screening for Vitamin D and B12 is Not Recommended
Based on the most recent 2024 Endocrine Society guidelines, routine screening for 25-hydroxyvitamin D should not be performed in the general population, and there is no guideline support for routine B12 screening in asymptomatic individuals 1.
Vitamin D Testing
When NOT to Test (Most Patients)
The 2024 Endocrine Society Clinical Practice Guideline explicitly recommends against routine 25(OH)D testing in 1:
- Healthy adults under 75 years
- Individuals with obesity
- Individuals with dark complexion
- General population screening
The rationale: No clinical trial evidence supports routine screening, no clear optimal target level exists for disease prevention, and empiric supplementation is inexpensive, safe, and feasible 1.
When Empiric Supplementation is Preferred (No Testing Needed)
Give vitamin D supplementation without testing to 1:
- Ages 1-18 years
- Adults over 75 years
- Pregnant individuals
- High-risk prediabetes patients
When Testing May Be Indicated
Testing should be reserved for established medical indications such as 1:
- Suspected vitamin D-related bone disorders
- Malabsorption syndromes (short gut, Roux-en-Y gastric bypass, terminal ileal disease)
- Nephrotic syndrome
- Conditions requiring monitoring of vitamin D metabolism
The 2015 USPSTF similarly found insufficient evidence to recommend for or against screening in asymptomatic adults 2.
Vitamin B12 Testing
No Guideline Support for Routine Screening
There are no current guidelines recommending routine B12 screening in asymptomatic individuals. The provided evidence does not include any guideline-level recommendations for B12 testing.
When to Consider B12 Testing
Based on clinical practice standards, test B12 when:
- Macrocytic anemia present
- Neurological symptoms (paresthesias, cognitive changes, ataxia)
- Malabsorption conditions (pernicious anemia, gastrectomy, terminal ileal disease)
- Strict vegan diet without supplementation
- Chronic metformin or PPI use with symptoms
Important Caveats
Test Variability Issues
Vitamin D assays have significant limitations 2:
- Variability between methods ranges 10-20%
- Classification as "deficient" varies by 4-32% depending on assay used
- No internationally recognized reference standard exists
- Misclassification can lead to overdiagnosis or underdiagnosis
The Association Between Vitamins D and B12
While research shows correlations between vitamin D and B12 levels 3, 4, 5, 6, this does not justify routine co-testing. These are observational associations without established causality, and they do not override the guideline recommendations against routine screening.
Cost Considerations
The cost-effectiveness of widespread vitamin D testing has been questioned, especially given uncertainty about optimal levels and the low cost of empiric supplementation 1. Testing rates have increased dramatically despite lack of evidence supporting this practice 2.
Practical Approach
For most patients: Skip testing and provide empiric vitamin D supplementation (600-800 IU daily for adults) if they fall into recommended groups 1.
Reserve testing for: Patients with specific medical conditions affecting vitamin D or B12 metabolism, or those with clinical signs/symptoms suggesting deficiency.