Circulating uncarboxylated matrix Gla-protein (ucMGP), in particular desphospho-ucMGP, is provided as a prognostic biomarker for allograft failure and mortality in patients who received organ transplantation and who are under immunosuppressive medication. A diagnostic tool is provided to monitor vitamin K status in such patients, i.e. the level of uncarboxylated species of extra-hepatic vitamin K-dependent proteins. Various forms and recommended dosages of vitamin K, optionally combined with vitamin D and/or other immunosuppressive medication, are provided to optimize the treatment of such patients resulting in decreased allograft failure and improved patient survival.
