Isoquercetin, a naturally occurring flavonoid glycoside derived from quercetin, has been investigated for its potential to reduce certain chemotherapy side effects, particularly chemotherapy-induced thrombosis and fatigue. Scientific validation for its use comes from a small but growing body of clinical and preclinical studies. Notably, a phase II randomized controlled trial published in Research and Practice in Thrombosis and Haemostasis (2019) found that isoquercetin supplementation reduced markers of hypercoagulability and the incidence of venous thromboembolism (VTE) in cancer patients receiving chemotherapy, compared to placebo. The proposed mechanism involves isoquercetin’s inhibition of platelet aggregation and its antioxidant, anti-inflammatory properties, which may help counteract some adverse effects of chemotherapeutic agents.

While these initial results are promising, the evidence is not yet robust. The trials conducted so far have relatively small sample sizes, and further large-scale randomized controlled trials are needed to confirm efficacy and safety. Anecdotal and preclinical data also suggest possible benefits in alleviating chemotherapy-induced fatigue and oxidative stress, but these findings remain preliminary. Importantly, isoquercetin is not a standard part of oncology guidelines, and its use should be considered experimental and supervised by healthcare professionals.

In summary, current scientific evidence suggests a potential role for isoquercetin in reducing specific chemotherapy-related side effects, particularly thrombosis, but more research is needed before routine clinical use can be recommended.