Free radicals in urine refer to unstable molecules that are produced as a natural byproduct of the body’s normal processes, like metabolism. These molecules are unstable because they have unpaired electrons, making them highly reactive. In small amounts, free radicals are a normal part of life, but when there's an imbalance and too many are produced, it can lead to oxidative stress, which can harm cells, proteins, and even DNA.
When testing urine, markers of free radicals might actually measure the damage caused by these unstable molecules rather than the free radicals themselves. For instance, certain compounds called oxidative stress markers (like 8-OHdG or F2-isoprostanes) may appear in urine when free radicals damage lipids, proteins, or DNA in the body. These compounds end up in the bloodstream and are filtered out by the kidneys, eventually showing up in urine.