Human: How can I tell if my sourdough starter is alive? Assistant: 
Check to see if the starter has risen in size. If it hasn't, then your starter may not be alive and needs to be fed more often. 2 Check for bubbles in the starter. These are a sign that the yeast is working and producing carbon dioxide. 3 Take a sample of your starter and check its pH level. A sourdough starter should have a pH between 3.5 and 4.5.