8-OHdG (8-hydroxy-2'-deoxyguanosine)

8-OHdG is a chemically damaged DNA building block, formed when reactive oxygen species (ROS) attack a specific spot on the guanine base. It is one of the most common and best-studied oxidative DNA lesions, in both your nuclear and mitochondrial DNA. When a repair enzyme (OGG1) cuts out the damaged base, the fragment ends up in your blood and then your urine. So urinary 8-OHdG (corrected for creatinine) is a non-invasive readout of oxidative DNA damage and repair. Levels rise with age, and run higher in smokers, people with obesity, and those exposed to radiation or pollutants. They are also consistently higher in patients with cancer, atherosclerosis, type 2 diabetes, and brain disease than in healthy controls (Wu et al., 2004). But these links are observational. 8-OHdG reflects your oxidative burden; it has not been shown to cause disease in humans, and antioxidants that lower it have not proven a clinical benefit. Measure it carefully: the reliable methods are LC-MS/MS or HPLC-ECD. Commercial ELISA kits can cross-react and substantially inflate the numbers (Korkmaz et al., 2018; Hu et al., 2004). And in prospective studies, urinary 8-OHdG tracks only weakly with age and does not reliably tell accelerated from normal aging, which limits its use as a standalone longevity marker (Mukli et al., 2022).

Last reviewed: June 22, 2026

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