Vitamin testing

Primary care

Vitamin testing

Primary care
In recent years, the number of vitamin D and B12 tests in the general practice has increased, often without an indication.

Increasingly, alleged vitamin deficiencies are associated with a broad variety of non-specific symptoms and complaints by patients. Due to this increased perceived importance of vitamin levels, at request of the patient, vitamin levels are increasingly tested by general practitioners without clinical indication. A lack of vitamin D and B12 rarely causes these symptoms.

Although the direct harmful effects are limited, this form of medicalization is undesirable. It supports irrational health perceptions in patients, leads to inefficient use of GP consultation and laboratory diagnostics and generates unnecessary healthcare costs.

This project aims to reduce Vitamin D and Vitamin B12 testing in primary care without clinical reason or indication.


A cluster randomized intervention study on the effect of a single de-implementation strategy (only GP information) or a double de-implementation strategy (GP and patient information) on the number of vitamin tests ordered was performed. 26 General practices from regional primary care networks of Utrecht (n=22) and Rotterdam (n=4) participated. All participating GPs were invited to two interactive training sessions and an e-learning about vitamin D and B12. In addition, they received their own application figures as mirror information every 3 months. Half of the practices also received patient information about vitamins D and B12: a video, a poster and leaflets for the waiting room. The number of performed vitamin D and B12 tests after one year was measured using the routine database of the regional laboratories and compared to a one-year pre-intervention period.

‘GPs found it motivating to receive benchmark information of all participating practices’


The total number of vitamins D and B12 tests decreased in both intervention groups. In the intervention group with only training for general practitioners, the number of tests decreased by 19% and 18% respectively. In the intervention group with also patient information about vitamins D and B12, the number of tests decreased by 29% and 22% respectively.

Specifically informing patients therefore helped to reduce the vitamin tests. The effect was strongest with practices that had the highest score before the intervention.


At the moment, this project is being completed. In the following years, this de-implementation strategy will be scaled up to other hospitals in the Netherlands.

Learn more:

In Dutch:

Contact us at


Saskia van Vugt, PhD, MD


Evelien de Schepper, PhD, MD

| ErasmusMC