We're reader-supported. If you buy through our links, we may earn a commission at no cost to you.

Here’s How to Test If Yeast Is Still Active

Found some old packets of dry yeast and wondering if it’s still active? Let’s talk about how to test it.

You were cleaning out your pantry and found a few old packets of yeast. But upon closer look, you saw that they were expired.

This brought up a question in your mind: How can you check if the yeast is still active? So you grabbed your phone, looked it up online, and ended up here.

Welcome, and know that you’re in the right place! We’ve taken to the test kitchen and put together this guide—complete with photos—to show you how to check if a packet of dry yeast is still active.

How to Check If Yeast Is Still Active

So, how can you check if the yeast in that packet is alive and kicking? Allow us to introduce you to a method that’s both easy and foolproof.

To check if dry yeast is still active, stir it in with lukewarm water in a cup or glass and let it sit for 5 to 10 minutes. If the water gets foamy and bubbly, then the yeast is alive and will make your bread rise. If not, the yeast cells are dead and you’ll need to use a different packet.

This test works for all types of dry baker’s yeast, including active dry yeast, instant yeast, and bread machine yeast.

Here’s what to expect:

A photo that demonstrates how to test if yeast is still active depicting a glass cup of dead yeast on the left and one with alive yeast on the right.
Dead yeast (left) compared to alive yeast (right)

As you can see in the photo, the dead yeast cells just float in the water and do nothing. The living yeast cells, however, wake up and start to bubble. In a few minutes, especially if it’s warm outside, the liquid will become foamy and start to rise in the cup.

You don’t really need much water—just enough to cover the yeast and, with a little stirring, turn it into a thick paste. If the recipe allows, you can also add ½ teaspoon of sugar (white, brown, cane; it makes no difference). Since yeast cells feed on sugar, this will speed up their activation.

It’s very, very important to make sure the water is lukewarm. If you use water that’s too hot, like from a kettle, or too cold, like from the fridge, it can kill the yeast cells and render the whole exercise useless.

Once you’re done with the test, simply work the foamy liquid to your dough mix and let it do its magic.

P.S. If the yeast turns out to be unusable, check out our tips on how to repurpose it instead of tossing it in our article, “Is It Okay to Use Dead Yeast?”

Know your author

Written by

Dim is a food writer, cookbook author, and the editor of Home Cook World. His first book, Cooking Methods & Techniques, was published in 2022. He is a certified food handler with Level 1 and Level 2 Certificates in Food Hygiene and Safety for Catering, and a trained cook with a Level 3 Professional Chef Diploma.