Kimberly White/GettyTheranos may be about to lose its partnership with the largest drug-retailing chain in the US. The Wall Street Journal is reporting that Walgreens, which operates more than 40 Theranos Wellness Centers — places where people can have their blood tested — out of its stores in Arizona and California, sent the blood-testing company a warning letter in late January that gave them 30 days to resolve the problems found with its lab in California or their partnership would be terminated.