CJC-1295 is a 30 amino acid peptide-based drug that stimulates the production of growth hormone (GH). It is unique among performance enhancing peptides due to the addition of a maleimidopropionic acid group to the lysine residue at the C-terminus. This reactive group allows the peptide to be covalently linked to sulfhydryl groups on the surface of plasma proteins. Once bound to the surface of a protein, CJC-1295 then functions as a protein-based drug rather than a peptide. As a result, CJC-1295 cannot be extracted from plasma by standard peptide SPE methods. Using monoclonal antibodies raised against the CJC-1295 peptide, we previously developed an immuno-PCR method to detect CJC-1295. Here we present a high-sensitivity ELISA method that detects CJC-1295-protein conjugate in plasma that is compatible with standard absorbance plate readers. The ELISA screen is highly sensitive and linear across the range from 12.5 pg/mL up to 400 pg/mL.