The study aims to evaluate the accuracy of two commercial glucose monitoring systems in patients with type 1 or type 2 diabetes and renal impairment, including patients with or without dialysis. Patients treatment experience will even be evaluated.

Continuous glucose monitoring (CGM) and Flash glucose monitoring (FGM) are tools today mainly used in the treatment of patients with type 1 diabetes. Both glucose monitors are subcutaneous tissue sensors, which provide a tissue fluid glucose measurement every 1 to 5 minutes. The real-time glucose sensor trend data can help patients with diabetes better manage their insulin needs with meals and exercise. The following glucose monitoring systems are two of the most current sensor technologies available for clinical use the Dexcom G5 (Dexcom Corporation), and the FGM (Abbot Freestyle Libre).

High glucose levels in patients with type 1 or 2-diabetes lead to increased risks of micro- and macrovascular complications, while low glucose levels may lead to unconsciousness. Therefore, it is important for patients to manage glucose levels as close to normal (4-7 mmol/l) as possible. This is generally performed by appropriate dosage of different insulins, calculated from the preprandial glucose level, carbohydrate intake, and physical activity. In spite of careful dosage, glucose levels often become too low or too high.

CGM is a novel tool to detect low and high glucose levels, and it is capable of sounding an alarm for low and high glucose levels. CGM has been available in clinical practice in Sweden for approximately 5 years. FGM is as CGM also a novel tool to detect low and high glucose levels, but is not capable of sounding an alarm for low and high glucose levels. FGM has been available in clinical practice in Sweden since late 2014.

Since both CGM and FGM measure the glucose level by a sensor in subcutaneous tissue, there is uncertainty in the estimation of blood glucose levels. The accuracy of a certain CGM or FGM system can be assessed by comparing the glucose levels estimated by the glucose monitors with measured glucose levels in capillary blood samples. To our knowledge there are no studies comparing the accuracy of the Dexcom G5 sensor with the Freestyle Libre sensor. In the current study, we will compare the accuracy and treatment experience of these two glucose monitoring sensors available on the market for clinical use in patients with type 1 or 2 diabetes and renal impairment with an eGFR<30 ml/min both in and not in dialysis.

Inclusion Criteria:

1. Type 1 or type 2 diabetes with renal impairment and eGFR <30 ml/min measured within the last three months.
2. Adult patients, age 18 or older and <80 years.
3. Written Informed Consent

Exclusion criteria:

1. Pregnancy
2. Patients with severe cognitive dysfunction or other disease which makes glucose monitoring use difficult.
3. Patients requiring continuous use of paracetamol. Paracetamol must not have been used the week before the study and shall not be used during the duration because it disturbs the interpretation of blood glucose levels estimated by the Dexcom G5. However, other pain killers can be used throughout the study period.
4. Current CGM or FGM use.
5. History of allergic reaction to any of the CGM or FGM materials or adhesives in contact with the skin.
6. History of allergic reaction to chlorhexidine or alcohol anti-septic solution.
7. Abnormal skin at the anticipated glucose sensor attachment sites (excessive hair, burn, inflammation, infection, rash, and/or tattoo).
8. Patients with renal impairment and eGFR greater or equal to 30 ml/min estimated by the MDRD formula.