Here we quantified ascorbic acid (AA) levels in 14 tissues, plasma and urine of C57BL/6 male mice to track its turnover during 3 to 30 mo of aging. The AA content of adrenal glands and testes decreased somewhat with age, and eventually rose, but increased in the spleen, lungs, eyes and heart. AA levels rose in the liver, skin and skeletal muscles from 6 to 12 mo of age, but declined from 12 to 24 mo. In the cerebellum, cerebrum, small intestine, kidney and plasma, amounts of AA remained almost constant as the animals aged. Most notably, urinary AA decreased markedly until becoming almost undetectable at 24 and 30 mo of age. Collectively, these results, which compare changes in AA levels in specific physiologic targets throughout the aging process, strongly suggest that the AA synthesizing capacity declines over time to become a major factor in senescence-related diseases.