3 week old starter

So I missed my brewday a few weeks ago and my 2 liter starter has been sitting in the fridge with a piece of foil covering the flask. I am brewing later today, should I still be ok using it?

 

I don't see a problem, smell it and if doesn't smell bad you're good to go

 

After 3 weeks in the fridge you have lost viability. How much I don't know. In a sense you are now pitching a smaller starter than your original.

I'm sure it will ferment your beer. If your original starter was optimum for your beer you are now underpitching. So it would be best to refresh the starter.

Since you are brewing later today you don't have many options. You could add a little wort and let it go as long as possible. If you have a LHBS you could get another vial. Or just pitch what you have.

 

Thanks for the input. I guess I can always make a lower gravity brew than I was planning and then just reuse the yeast for an imperial stout.

 

I've had starters that have sat a few weeks. My fermentation still took off within a few hours, and I didn't notice any off flavors.