8-OHdG
Also known as: 8-Hydroxy-2-deoxyguanosine, Oxidative DNA Damage Marker
What Does 8-OHdG Measure?
8-OHdG (8-Hydroxy-2-deoxyguanosine) is a biomarker that measures oxidative damage to DNA. When reactive oxygen species (free radicals) attack DNA, they most commonly target guanine — one of the four DNA bases — converting it into 8-OHdG. This damaged nucleoside is then excised from DNA during repair processes and released into the urine and blood, where it can be measured. Elevated levels indicate that the body's DNA is under significant oxidative stress and that repair mechanisms are actively working to correct the damage.
Why Does 8-OHdG Matter?
8-OHdG is considered one of the most reliable and sensitive markers of oxidative DNA damage and overall oxidative stress in the body. High levels are strongly associated with accelerated cellular aging, increased cancer risk, cardiovascular disease, neurodegenerative conditions such as Alzheimer's and Parkinson's disease, and metabolic disorders including type 2 diabetes. Because DNA damage is a fundamental driver of cellular dysfunction and chronic disease, monitoring 8-OHdG provides a window into long-term health trajectories that many conventional lab tests cannot capture. It is widely used in research and increasingly in functional and preventive medicine to assess the efficacy of antioxidant therapies and lifestyle interventions.
Normal Ranges
Males
< 15 ng/mg creatinine (urine); < 0.5 ng/mL (serum/plasma) — values vary by laboratory method
Females
< 15 ng/mg creatinine (urine); < 0.5 ng/mL (serum/plasma) — values vary by laboratory method
Children
Generally lower than adults; reference ranges vary significantly by age and laboratory
Causes of High Levels
- Chronic oxidative stress from poor diet high in processed foods, trans fats, and refined sugars
- Smoking and exposure to secondhand smoke or environmental pollutants (heavy metals, pesticides, air pollution)
- Chronic inflammatory conditions such as obesity, metabolic syndrome, type 2 diabetes, and autoimmune diseases
- Intense or prolonged physical exercise without adequate antioxidant support or recovery
- Radiation exposure (UV radiation, ionizing radiation from X-rays or medical imaging)
- Mitochondrial dysfunction leading to excess reactive oxygen species (ROS) production
Causes of Low Levels
- High dietary intake of antioxidant-rich foods such as fruits, vegetables, and polyphenol-containing foods
- Regular, moderate aerobic exercise which upregulates endogenous antioxidant defenses (superoxide dismutase, catalase, glutathione)
How to Improve Your 8-OHdG
Diet
- Increase consumption of colorful fruits and vegetables rich in antioxidants — aim for 7–10 servings daily, emphasizing berries, leafy greens, and cruciferous vegetables
- Incorporate green tea (2–3 cups/day) for its high EGCG content, which has been shown to reduce 8-OHdG levels in clinical studies
- Reduce processed meats, refined carbohydrates, and trans fats which promote lipid peroxidation and oxidative DNA damage
- Include omega-3 fatty acid-rich foods (wild salmon, sardines, flaxseed, walnuts) to reduce inflammation and oxidative stress
- Consume lycopene-rich foods such as cooked tomatoes and watermelon, which have demonstrated DNA-protective effects
Supplements
- Vitamin C: 500–1000 mg/day — a water-soluble antioxidant that neutralizes free radicals before they can damage DNA
- Vitamin E (mixed tocopherols): 200–400 IU/day — protects cell membranes and DNA from lipid peroxidation
- CoQ10 (Ubiquinol form): 100–300 mg/day — supports mitochondrial efficiency and reduces ROS production at the source
- N-Acetylcysteine (NAC): 600–1200 mg/day — precursor to glutathione, the body's primary intracellular antioxidant
Related Biomarkers
Frequently Asked Questions
How is 8-OHdG tested and where is the sample collected from?
8-OHdG is most commonly measured in a 24-hour urine sample or a first-morning spot urine collection, where results are expressed relative to creatinine concentration to account for urine dilution. It can also be measured in blood (serum or plasma), though urine testing is generally considered more practical and reflective of systemic DNA repair activity. Some research labs also measure 8-OHdG directly in white blood cell DNA for a more tissue-specific assessment. Testing is most widely available through functional medicine practitioners and specialty laboratories.
Is high 8-OHdG a sign of cancer?
Elevated 8-OHdG is not a direct diagnosis of cancer, but it is recognized as a significant risk factor and early warning signal. Oxidative DNA damage is a key initiating step in carcinogenesis — when DNA damage accumulates faster than it can be repaired, it can lead to mutations that drive uncontrolled cell growth. Studies have found elevated 8-OHdG in patients with lung, breast, liver, kidney, and colorectal cancers. However, high levels may also result from many non-cancerous conditions including diabetes, inflammation, and smoking. If your levels are elevated, discuss with your doctor to identify and address the underlying causes.
Can I lower my 8-OHdG levels through diet and lifestyle changes?
Yes, multiple clinical studies have demonstrated that 8-OHdG levels are responsive to diet and lifestyle changes. Interventions that have shown measurable reductions include a diet rich in antioxidants, green tea consumption, supplementation with vitamin C and E, regular moderate exercise, smoking cessation, and reducing exposure to environmental toxins. Many studies show significant reductions in 8-OHdG within 4–12 weeks of sustained lifestyle changes, making it a useful biomarker for tracking the effectiveness of health interventions.