Hyperphosphatemia is a common problem among patientens suffering from chronic kidney disease. Hyperphosphatemia is associated with increased risk of cardiovascular diseases. One of the treatments are through the diet, where patients are instructed ind reducing their daily intake of phosphate. But since phosphate exists in both organic and inorganic forms in the diet, this leads to several problems. Informations of the bioavability and furthermore the effect of plasma koncentrations of phosphate are lacking for both forms of phosphate.

Inclusion Criteria:

• Patients > 18 years
• Competent
• The patient should be able to take a sample of p-fluid and urine by himself
• Chronic peritoneal dialysis
• Reads and understand danish
• Has been informed written and oraly about the study and signed informed consent
• P-phosphate koncentrations 0,7-2,0 .mol/l
• P - ioniset calcium 1,1-1,4 mmol/l

Exclusion Criteria:

• Pregnant or breast-feeding
• Terminal patients
• If the experience acute infections or other acute situations they will be excluded from the study