It is used medically to determine calcium levels in the human body, or to synthesize polyamides or polyimides.

o-Cresophthalein has been used to derive polyamides and polyimides, colorimetrically estimate calcium in serum, and predict amount of time to wait before blood collection after a patient receives gadodiamide.

[2] The diether-diamine 3,3-bis[4-(4-amino-phenoxy)-3-methylphenyl]phthalide, or BNMP, is synthesized by 12 g o-cresophthalein, 11.5 g p-chloronitrobenzene, 5.1 g anhydrous potassium carbonate, and 55 mL of DMF.

It should then be recrystallized from glacial acetic acid to yield yellow needles.

The required liquid complexone is made by dissolving 10 mg o-cresolphthalein complexone in 50 mL alkaline borate[clarification needed], and then 50 mL of 0.05 N HCl are added to make the solution's pH 8.5.

Calcium in the body should be determined accurately to ensure that the Gadodiamide does not have adverse effects on the patient.

For these methods, glomerular filtration rate, or GFR, and time since gadodiamide was given should be recorded.

Ultimately, these two factors and the impact of gadodiamide on calcium levels calculated by the o-cresolphthalein method helps to reveal an amount of time that patients must wait after receiving gadodiamide to have blood drawn again, or avoid pseudohypocalcemia.

[4] To the left is the NFPA diamond as determined by the Safety Data Sheet, or SDS, by Fisher Scientific.