If it was me, id call in, and explain.... with it being a Saturday you'll no doubt get the 'yeh, yeh, where are you off to this evening then?' But thats to be expected...
If you turn up sick, try and hide it, and infect others on board, you'll be called in to the bosses office for sure.... Easier to put up with the phone banter, go to the docs on Monday morning and send them a late sick chit.
I always think... Not that im ever sick (unfortunately) but its not just you at risk if you turn up to fly with a cold/flu.