Late to work today

I was late to work today because just as I was about to leave, I started feeling not so good at all, and needed to just stay sitting down.
I got a bad cramp, and nauseated.
I knew it wouldn't last long, and it wasnt that terrible, but it was frustrating because I just couldn't go to work until it was over (which took about 20 minutes).
I feel fine now, for the most part.
Luckily, my boss knows whats up.