The hematocrit level is defined as the ratio of plasma volume and red blood cell mass. Determination of this level is important for the diagnosis and follow-up of various hematological and renal disorders. In clinical practice, automated hematology analyzers are commonly used.

Recently, a new method for hematocrit level determination has been introduced which employs layered resonant piezoelectric sensors. In the present study this technique will be applied in blood samples of healthy subjects and compared to a standard laboratory method.

Inclusion Criteria:

• Men and women aged between 18 and 80 years
• Men and women will be included in equal parts
• Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant

Exclusion Criteria:

• Symptoms of a clinically relevant illness in the 3 weeks before the study day
• Systemic treatment with anticoagulants
• Intake of any medication that could lead to spurious hematocrit values
• Presence of any medical condition that could lead to spurious hematocrit values
• Blood or plasma donation during the previous 3 weeks