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NAD+is an essential coenzyme for all living cells. NAD+concentrations decline with age, but whether this reflects impaired production or accelerated consumption remains unclear. We employed isotope tracing and mass spectrometry to probe age-related changes in NAD+metabolism across tissues. In aged mice, we observed modest tissue NAD+depletion (median decrease ∼30%). Circulating NAD+precursors were not significantly changed, and isotope tracing showed the unimpaired synthesis of nicotinamide from tryptophan. In most tissues of aged mice, turnover of the smaller tissue NAD+pool was modestly faster such that absolute NAD+biosynthetic flux was maintained, consistent with more active NAD+-consuming enzymes. Calorie restriction partially mitigated age-associated NAD+decline by decreasing consumption. Acute inflammatory stress induced by LPS decreased NAD+by impairing synthesis in both young and aged mice. Thus, the decline in NAD+with normal aging is relatively subtle and occurs despite maintained NAD+production, likely due to increased consumption.