GC Agar is used with hemoglobin and enrichment for the isolation and cultivation of Neisseria gonorrhoeae and other fastidious organisms in a laboratory setting. GC Agar II is not intended for use in the diagnosis of disease or other conditions in humans.

In 1945, Johnston described a medium that grew N. gonorrhoeae in 24 rather than 48 hours. GC Agar was introduced in 1947 with reduced agar content. While investigating the growth rate of gonococcus, a medium containing growth factors glutamine and cocarboxylase improved recovery. In 1964, Thayer and Martin formulated a medium incorporating the antibiotics Polymyxin B and Ristocetin, with added supplements, into GC Agar. Thayer and Martin improved their medium by replacing the antibiotics with a new solution of Colistin, Vancomycin, and Nystatin (CVN). In 1970, Martin and Lester improved the new Thayer-Martin Medium by increasing the agar and glucose, and adding Trimethoprim Lactate (T), calling it Modified Thayer-Martin (MTM) Medium. Martin and Lewis improved selectivity of MTM by increasing the concentration of Vancomycin and replacing Nystatin with Anisomycin for greater inhibition of yeasts, known as Martin Lewis (ML) Agar.

• Platform: dehydrated culture media
• Formula: enzymatic digest of casein 7.5g/L, haemoglobin solution 2% 100mL, enzymatic digest of animal tissue 7.5g/L, growth enrichment 2mL, corn starch 1.0g/L, antimicrobials if required, dipotassium phosphate 4.0g/L, monopotassium phosphate 1.0g/L, sodium chloride 5.0g/L, agar 10.0g/L
• Grams per litre: 70.20
• Litres per 500g: 22.90
• Plates per 500g: 1,526.00