Is my sourdough starter dead? How to tell, and how to bring it back

You open the fridge and find a jar of gray liquid sitting on a flat, sour-smelling paste. It's been weeks. Is it gone?

Almost certainly not. King Arthur Baking is blunt about it: a mature starter is very hard to kill by neglect. Left unfed, it goes dormant, and a few feedings usually wake it up. The real question is whether it's merely hungry, or whether something else has moved in. Those look different, and it's worth knowing which is which.

Signs it's just hungry

These all look alarming and are all normal for a starter that's run out of food:

• Liquid on top. This is called hooch. It's a byproduct of fermentation and a sign of hunger, not spoilage. It can be clear, gray, brown or black. Stir it back in, or pour it off if there's a lot of it or it's very dark.
• It's flat and won't rise. It ate everything and stopped. Feeding fixes this.
• It smells sharp. Alcohol, vinegar and even nail-polish remover (acetone) smells are hunger signals. King Arthur's newest guide says a starter that smells like nail-polish remover isn't spoiled, just hungry.
• A dark, dry skin on top. After several months, a gray crust can form. Peel it off and throw it away. The starter underneath is fine. This is a dried layer, not mold.

Signs you should throw it out

Some signs mean the starter is contaminated, and no amount of feeding will make it safe:

• A pink or orange tint or streaks, anywhere in the starter.
• Fuzzy mold of any colour, white, black, blue or green.
• Colours other than cream or amber outside the hooch, in the pink, blue, green or orange range.
• A putrid smell. Not sour or boozy, but rotten, like garbage.

Don't scrape the mold off and keep going. King Arthur says to throw out any starter with mold. Colorado State University Extension says a starter with coloured or fuzzy mold shouldn't be used, and the container should be cleaned. University of Illinois Extension also says to discard it. As the USDA notes about soft, moist foods in general, mold can reach below what you can see.

One nuance: Colorado State notes that whitish clumps floating on the liquid of an unfed fridge starter are usually harmless yeast. The rule of thumb that keeps you safe is simple. If it's fuzzy, throw it out.

How to bring a dormant starter back

This is the method King Arthur Baking recommends:

1. Stir in or pour off the hooch.
2. Keep 50 g of the starter and discard the rest.
3. Add 50 g of flour and 50 g of warm water, and stir well.
4. Mark the level on the jar with a rubber band or tape.
5. Leave it for 12 hours, ideally somewhere around 75–78°F (24–26°C).
6. Look for any rise or bubbles. Either means it's alive.
7. Repeat every 12 hours until it doubles within 12 hours.

It's ready to bake with when it doubles within about 6 to 8 hours of a feeding.

For a starter that's been badly neglected, King Arthur suggests two extras: use whole-grain flour for half of the flour in each feeding, and throw away the discard from the first revival feeding rather than baking with it.

How long can a starter go without feeding?

There's no official limit, only examples. King Arthur has revived:

• a starter left unfed at room temperature for a month, back to normal in three to four days;
• a starter left in the fridge for eight weeks, back within a few days;
• a starter forgotten for more than six months.

After a year or more, a starter can dry into a chalky block. The longer it sat, the longer it takes to wake up. If you've fed it every day for three or four days and seen no response at all, start fresh.

When it really is dead

A neglected starter can show no life for the first several feedings and still recover, so give it time. If it still shows no bubbles and no rise after three or four days of regular feedings, it has probably died. Heat can also kill it. Yeast dies at around 140°F (60°C), so a starter forgotten in the oven when it's switched on won't come back.

A note on tasting

It's tempting to taste a starter to check it. Don't. Colorado State University Extension says not to taste raw starter, and King Arthur's 2026 guide says not to eat it. The CDC and FDA warn more generally against eating raw flour or raw dough, because flour can carry E. coli and Salmonella until it's baked or cooked. Use your eyes and nose instead.

How we handle this in Sourdough Starter Tracker

Our app was built around the question in this post's title. When you log a feeding, you can note how your starter smells. A hungry smell like vinegar or acetone gets a nudge to feed. A smell that can mean trouble gets a red warning to check for mold, fuzzy growth and pink or orange streaks, so a real problem doesn't look like a tip. Reminders follow your schedule, so the jar is less likely to end up forgotten in the first place.

Sources

• King Arthur Baking: Do you think you killed your sourdough starter?, Forgot to feed your sourdough starter?, Liquid on top of your starter, Sourdough starter troubleshooting and part 2, Sourdough Tips and Recipes (2026)
• Colorado State University Extension: Sourdough starter best practices
• University of Illinois Extension: Sourdough 101
• USDA: Molds on food: are they dangerous?
• CDC: Don't eat raw dough · FDA: Handling flour safely