But Negouai is a Muslim and has been asked in the middle of Ramadan, the month where Muslims are forbidden to eat or drink between dawn and sunset.
The Frenchman has therefore been forced to compromise his religious beliefs and Keegan has promised to take the matter up with UK Sport.
"He had to drink water to get a sample and didn't want to do it," said the City boss. "On the one hand I am saying to him: `If you don't take it, it looks very suspicious,' but on the other it is his belief, his religion."
"There are times when professional football and religion cross over. We had another case this week because of what happened with Christian he gets drug tested three or four times.
"I am going to have to talk with UK Sport. If we are honest Christian is very upset. We all have to be understanding, I am going to have a chat with him because they will probably test him again."