Guardant Health Shield is a proprietary blood test designed to identify genomic and epigenomic alterations in cell‐free DNA and proteomic changes in plasma for early detection of colon cancer.^1‐3 The test aims to detect methylation sequences in circulating tumor DNA (ctDNA) present in the bloodstream.^1,2 Although not studied for screening, ctDNA has been studied to assess the benefit of adjuvant chemotherapy after colorectal cancer surgery.⁴ Other early‐detection blood tests for cancer are available, although none have been approved by the U.S. Food and Drug Administration (FDA).⁵ Shield is not a replacement for currently recommended colorectal cancer screening methods and does not have FDA approval.⁶