Micronutrient, Vitamin C

Vitamin C is an essential nutrient your body cannot make on its own, so it must come from your diet—mainly fruits and vegetables like citrus, strawberries, and bell peppers. It helps your body build and repair tissues, supports your immune system, and acts as an antioxidant to protect your cells. Low levels can cause symptoms like fatigue, easy bruising, slow wound healing, and in severe cases, a condition called scurvy. Most people get enough vitamin C through a balanced diet, but certain groups—such as smokers, older adults, or people with digestive conditions—may be at higher risk for deficiency. Your healthcare provider can help interpret your results in the context of your overall health and diet.

When elevated: Elevated plasma vitamin C levels are generally not associated with significant clinical toxicity at physiologic doses; however, very high supplemental intake (>2 g/day) may increase the risk of oxalate nephrolithiasis, gastrointestinal disturbances, and, in individuals with hemochromatosis or G6PD deficiency, may exacerbate iron overload or hemolysis respectively. Supraphysiologic levels are typically transient due to renal excretion. When low: Low vitamin C levels indicate inadequate intake or increased utilization and are associated with impaired collagen synthesis, increased capillary fragility, poor wound healing, and compromised immune function. Severe deficiency causes scurvy, while subclinical deficiency may contribute to fatigue, depression, and increased oxidative stress. Deficiency has been associated with increased cardiovascular risk in observational studies, though causality has not been firmly established.

Vitamin C supports collagen synthesis and immune function, both critical for athletes managing training stress and recovery. Intense exercise increases oxidative stress and infection risk; adequate vitamin C helps neutralize free radicals and maintain immune resilience during heavy training blocks.