True degradation of NAD⁺ (the oxidised form) involves a chemical breakdown typically triggered by prolonged exposure to heat, light, or moisture. However, a slight yellowish tint in a formulation does not necessarily indicate degradation.

This colour change can result from minor oxidation—such as trace formation of NADH, which absorbs light at 340 nm—as well as the presence of excipients, stabilisers, or other harmless formulation components. Additionally, natural variation in raw materials from different manufacturing sources can influence appearance. Importantly, degradation cannot be confirmed by visual inspection alone and must be verified using analytical methods such as HPLC, UV-Vis spectrophotometry, or mass spectrometry.

A yellowish hue in NAD⁺ does not indicate impurity or reduced quality. Many GMP-compliant suppliers produce NAD⁺ that meets or exceeds 98% purity, as verified by HPLC, with demonstrated stability under ICH storage conditions and confirmed bioactivity.

Regulatory standards such as those from the United States Pharmacopeia (USP) permit certain colour variations, provided that assay results confirm the compound’s identity and potency. As highlighted in sources including Ying (2008), Sigma-Aldrich specifications, and the USP–NF monograph, visual appearance alone is not a reliable indicator of degradation. O

Only validated laboratory assays can accurately determine the integrity of NAD⁺. Relying solely on visual inspection risks misinterpretation and unnecessary product rejection. Ultimately, visual colour is a cosmetic property — true purity and potency come from the data.