Continuous monitoring of the skin tissue glucose concentration on two different study days using glucose sensors that work on the principle of impedance spectroscopy, with systematic alteration of the blood glucose concentration using the glucose clamp technique in healthy subjects and subjects with type 1 diabetes. Simultaneous determination of electrolyte concentrations in the blood by taking frequent blood samples.

A completely non-invasive continuous glucose monitoring device is considered as a major target of glucose sensor development. The aim of this study is to evaluate the performance of a non-invasive glucose sensor (wristwatch) under controlled conditions (glucose clamp) at hyperglycemia (study day 1) and at hypoglycemia (study day 2). Measurements of the non-invasive glucose monitoring device are compared to those obtained from a minimally invasive glucose monitoring device (GlucoDay, microdialysis principle). In addition, changes in blood electrolyte concentrations as well as their impact on the measurements of the non-invasive glucose sensor are evaluated.

Inclusion Criteria:

Healthy male and female volunteers:

• Written informed consent
• Aged between 18 and 40 years
• Body mass index between 18 and 28 kg/m²
• Haemoglobin > 13 g%

Male and female patients with type 1 diabetes:

• Known type 1 diabetes, first manifestation 6 months to 15 years before the start of the study
• HbA1c <= 9%
• Written informed consent
• Aged between 18 and 40 years
• Body mass index between 18 and 28 kg/m²
• Haemoglobin > 13 g%

Exclusion Criteria:

• Uncontrolled arterial hypertension (diastolic blood pressure >100 mmHg and/or systolic blood pressure > 180 mmHg)
• For women, pregnancy or breast-feeding or, for sexually active women of child-bearing age, the use of contraceptive methods considered to be safe (oral contraceptives, IUD, implanted or injected contraceptives, diaphragms, or surgical sterilisation of the patient or her partner)
• Deviations in the lab values (excluding HbA1c), as judged by the investigator to be clinically significant, in particular an increase in transaminases to a level that is two and a half times higher than the upper normal value and a creatinine value that is above the normal range
• Severe acute diseases, as judged by the investigator
• Severe chronic disease, as judged by the investigator
• History of macrovascular illnesses such as pAVK, myocardial infarction
• Known microvascular (diabetic) complications (other than diabetic background retinopathy)
• Positive serology for hepatitis B, hepatitis C or HIV
• Blood donation within 3 months prior to the start of the study and intention of donating blood within 3 months after the end of the study