In healthy subjects: Continuous monitoring of the glucose concentration in the skin by means of a non-invasive glucose sensor during a glucose clamp when systematically changing the blood glucose concentration (e.g. to hyperglycemia). Simultaneous frequent determinations of serum electrolytes.

Non-invasive continuous glucose monitoring is a promising approach in diabetes therapy. It is known that changes in glucose concentration in the skin can be registered by means of optical, spectroscopic measures in subjects with diabetes. The precision of such measures, however, so far has been unsatisfactory.

This study evaluates the changes in skin glucose concentration by means of a non-invasive glucose sensor and compares these to blood glucose concentrations during a glucose clamp. It is also known that with hyperglycemic blood glucose concentrations there is a consecutive hyponatraemia. This study shall evaluate to which extent and how fast serum electrolyte parameters change when establishing a hyperglycaemic blood glucose level. This shall help estimate which impact these changes in electrolytes have on the non-invasive glucose sensor.

Inclusion Criteria:

• Written informed consent
• Age between 18 and 65 years

Exclusion Criteria:

• Uncontrolled hypertension (diastolic blood pressure > 100 mmHG and/or systolic blood pressure > 180 mmHg)
• Pregnancy or lactation period for female subjects
• Serious clinical signs of a liver disease, acute or chronic hepatitis, acute or chronic kidney disease, or ALAT > 2.5 times the upper level of normal values, or serum creatinine > 1.3 mg/dL (women)/1.5 mg/dL (men)
• Any serious acute illness (at the decision of the investigator), e.g. sepsis, gastric or duodenal ulcer, acute myocardial infarction, acute asthma attack
• Any other serious chronic illness (at the decision of the investigator), e.g. chronic obstructive pulmonary disease, any kind of cancer