High milligram testosterone gives lots of people test flue. Apparently it’s the solvent to keep it suspended that affects people. I had it once from infection 2ml of test 250 and it was not that bad. Not like having a real flue. Lots of people got test flue last year when TestE was a yellow colour not clear. A lot of bad powder was coming out of China at the time.
People getting really sick and going to hospital.
So to answer the question. Bad gear and good gear can cause test flue.