Serum creatinine (Scr) is the most commonly used biomarker of kidney function. In the steady-state, serum creatinine can be used to estimate glomerular filtration rate, using the modification of diet in renal disease (MDRD) [1] or chronic kidney disease epidemiology collaboration formulae.
Doses up to 25 grams daily for up to 14 days have been safely used. Lower doses up to 4-5 grams taken daily for up to 18 months have also been safely used. Creatine is POSSIBLY SAFE when taken by mouth, long-term. Doses up to 10 grams daily for up to 5 years have been safely used.