I am in the same situation.

1 hour before the test, I took a pee, and at the time of the test,
I was running on an empty bladder.

Being scared that I'd have nothing for them, I drank a cup of water and ate
a grapefruit.

Well, the assholes over there had me wait 1 hour, just to pee in a cup, and my bladder was FULL. I was ready to pop. They gave me the cup and it was mildly clear, with a hint of yellow.

I don't think nothing of it, hell I'm clean. I come home and smoke a joint, and now I'm paranoid about it coming back diluted.