A single centered, prospective, double blinded study enrolling 12 Type I diabetic patients (+ up to 4 replacements) in two cohorts. Patients will wear multiple FiberSense CGM systems for 28 days, with total duration of the participation up to 8 weeks (screening + active phase + follow up).

The primary aims of the study are assessment of the safety and tolerability of the FiberSense CGM system during the wearing time together with characterization of the system performance when compared to capillary blood samples.

The FiberSense system is intended to be used by diabetic patients in a home use setting as a CGM system using the interstitial fluid (ISF) glucose as an indicator of blood glucose levels.The purpose of this study is to assess the performance of FiberSense system across the glucose measurement ranges as compared with a laboratory standard reference method in diabetic patients (Type I) during in-clinic glucose challenge sessions. At the same time and also at home use the blood glucose values are recorded by comparator system and self-monitoring blood glucose system (SMBG). The safety aspects are also investigated during the wearing time of 28 days.

The two cohorts differ in the measurement scheduled, with intensive measurement week either at week 1 (cohort A) or week 2 (cohort B).

Inclusion Criteria:

1. Male or female age ≥ 18 and < 65 years old.
2. Diabetes mellitus type I requiring insulin in the management of glucose control for at least one year prior to enrollment.
3. Women who are not pregnant, lactating or planning a pregnancy during their participation in the clinical study. If of child bearing potential, the patient must agree to abstain from sexual intercourse or use reliable forms of contraception (e.g. condom or diaphragm with spermicide or oral contraceptives) to prevent pregnancy for the length of the clinical study.
4. Willingness, ability and commitment to comply with the testing, procedure and follow-up outlined in this protocol including (but not limited to) frequency of clinic visits, use of pre-specified glucose monitoring devices.
5. In the opinion of the investigator, absence of any physical limitations, addictive diseases, or underlying medical conditions (including mental health) that may preclude the patient from being a good study candidate.
6. For the time of the wearing phase willingness to abstain from taking a sauna, bathing, swimming, diving and contact sport activities.
7. Fully vaccinated with EMA approved vaccine against SARS-COV-2 virus or recovered from Covid-19 disease, (status vaccinated or recovered according to current Corona regulations as recommended by STIKO). If applicable, a negative result of a current Corona test (depending on the guidelines of the study center).
8. Written informed consent to participate in the study provided by the patient.

Exclusion Criteria:

1. Persons who use medication containing icodextrine or maltose and which can result in icodextrine or maltose present in blood (dialysis solutions, antibody medications etc.), anamnesis based.
2. Persons on peritoneal dialysis.
3. History of significant hypoglycemia unawareness, or a history of severe hypoglycemia (requiring emergency medical intervention) within the last 6 months.
4. Currently pregnant, as demonstrated by a positive pregnancy test at screening and/or Day00 prior to enrolment.
5. Any active acute or chronic infectious disease that, in the opinion of the investigator, might interfere with the performance of this study or would pose an excessive risk to study staff (e.g., Hepatitis B and C, HIV, Covid-19).
6. Extensive skin changes/diseases that preclude wearing the required number of devices on normal skin at the proposed application sites (e.g., extensive psoriasis, recent burns or severe sunburn, extensive eczema, extensive scarring, extensive tattoos, dermatitis herpetiformis).
7. Have a known allergy to medical-grade adhesives, or known hypersensitivity to any of the products used in the study.
8. Blood donation of more than 500 ml within the last three months or hematocrit value <30% or > 50%.
9. Currently participating in another investigational study protocol where the testing or results may interfere with study compliance, diagnostic results, or data collection.
10. Has a MRI scan, CT scan, diathermy or a flight scheduled during the proposed study participation.
11. Has vaccination/booster against COVID-19 scheduled during or less than 2 weeks prior to the proposed study participation.
12. An identified protected vulnerable patient (including but not limited to those in detention, or a prisoner).