In the diagnosis of a deficiency in vitamins, minerals or trace elements, investigative skills are often required: risk factors for a deficiency and deficiency symptoms lead to a suspicion which can then be verified by a blood test or an attempt at therapy.
A suspected diagnosis can be verified by means of a blood test. Here, the concentrations of the biofactors which may be critical, e.g. in plasma, serum or whole blood, are measured or sensitive biomarkers determined. As a rule, the costs of the blood test are not paid for by the statutory health insurance companies. And: it is not always possible to reliably detect a deficiency by means of a blood test.
A less scientific method, but one which is crucial for the patient is whether after an increase in the supply of suspicious biofactors, the symptoms become better. In this manner it is possible to draw a subsequent conclusion of a deficiency that previously existed.