Are My Kefir Grains Dead?

By Nik, founder of 東歐嚴選｜kefir.link and former chef · First published 25 July 2024 · Updated 3 November 2026

The milk is still runny after a day. The grains look smaller, or a little yellow, or slimy. They haven’t grown all week. Are they dead? Almost always, they are fine. Kefir grains are tougher than they look, and most “dead” grains are only tired after shipping, a rest in the fridge or a hot day. Here is how to tell the difference, and how to bring them back.

The short answer

• Fermentation is the real test. If the milk thickens and turns sour within about 24–36 hours, your grains are alive, whatever they look like.
• Slow growth is normal. 10 g of grains can take one to three weeks to double. Keep feeding them through a few days without growth.
• White, cream, beige or light yellow is normal. Pink, red, orange, green, blue, grey, black or fuzzy patches are mould: throw away the grains and the milk.
• Tired grains need a few batches. After shipping or the fridge, use less milk for the first three batches and keep them at about 24°C.
• Room temperature is all they need. Keep grains below 35°C and ferment them in a jar at room temperature, away from yogurt makers, rice cookers and ovens.

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Quick check: dead, tired or just over-fermented?

How we checked this guide

• Our care guide and our customers: the method comes from the printed care guide that ships with our grains, and from years of customer questions on LINE: “Did it work?”, “How do I read the pH strip?”, “Why aren’t they growing?”.
• Food-safety guidance: the British Columbia Centre for Disease Control’s kefir guidance (2024) and US university extension guides, for the pH and timing safety limits.
• Published research: studies that weighed kefir grains batch after batch in cow’s milk and soy milk, linked next to the sentences they support.

1. Does the milk still ferment?

This is the one sign that really matters. Living grains turn milk into kefir: it thickens, starts to separate and smells pleasantly sour.

• Normal timing: about 24 hours at room temperature, ideally about 24°C. In winter or a cool room it can take longer.
• Not thick after 24 hours? Close the jar and let it continue for up to 36 hours in total.
• Still like milk after 36 hours? Strain out the grains, pour that milk away and start again with less milk, worked out in the kefir calculator with “Sleepy” grains.
• When to start fresh: after about five failed batches in a row with less milk and a room at about 20–26°C, start again with fresh grains.

Checking with a pH strip

Fresh milk is about pH 6.6. As the grains ferment it, the pH drops. Food-safety guidance says finished milk kefir should reach pH 4.6 or lower within 36 hours (BC Centre for Disease Control, kefir guidance); well-fermented kefir is usually about 3.5–4.2.

• Mix first: gently stir the kefir, because the layers have different acidity.
• One drop: put one drop on the strip with the dropper and read the evenly wet ring around the drop.
• Timing: test after 12–24 hours of fermenting.
• Soy milk: judge soy kefir by how thick it is, because its acidity changes very little.

Want an exact number? Read Did your milk kefir work? Test it with a pH meter.

2. Are they growing?

Healthy grains slowly increase when they get fresh whole milk every day. Growth is slow and uneven, so give them time.

• How slow: in laboratory studies, grains grew about 6% a day, roughly 1.6 times in a week (study). At home, 10 g usually takes one to three weeks to become 20 g.
• What slows growth: the first days after shipping or the fridge, rooms above 30°C, plant milk, low-lactose milk, and rinsing the grains with water.
• When to start fresh: if a month passes without growth and fermentation stays weak, start again with fresh grains.

Weigh them once a week; weekly changes are easier to see.

3. Colour and smell

• Keep everything dry: pink patches almost always start with water. A wet jar, strainer or spoon, or grains rinsed under the tap, lets other microbes in. Dry everything completely before it touches the grains.
• A thin white layer on top is usually yeast, which is normal. Read Is the white layer on kefir mold?

4. Slimy, floating or smaller grains

• Slimy or stringy: a good sign. The grains make a soft gel called kefiran that holds the bacteria and yeasts together (review). Leave it on the grains.
• Floating: normal. Bubbles from the yeasts lift the grains to the top.
• Small or broken pieces: normal. Grains range from a grain of rice to large flat sheets, and small grains ferment just as well. See Kefir Grains 101: size, shape and color.
• Hard, dry or powdery with no fermentation: start fresh with new grains.

5. Over-fermented kefir means busy grains

If the grains have too little milk, or the room is warm, they finish early and keep going. You get a lot of clear yellowish liquid and thick white curds that look more like cheese than soft tofu.

• The liquid is whey, the watery part of milk. It is natural; stir it back in or strain it off.
• The grains are healthy, in fact very active.
• The kefir is still fine to drink if it fermented about a day and a half at most. It will be sourer; honey or fruit help. Throw away a jar that sat forgotten at room temperature for several days.
• Next batch: more milk, fewer grains or a shorter time. Our kefir calculator works out the amounts for your room temperature.

How to revive tired grains

After shipping, a rest in the fridge or a hot spell, grains need a few batches to wake up. The first batches may be thin; that is expected.

1. Strain them and rinse them with fresh milk. Pour away the liquid they came in.
2. Use less milk for the first three batches. Work out the amount in the kefir calculator with “Sleepy” grains. Then increase slowly.
3. Keep them at about 24°C, out of direct light. Let fridge-cold milk warm up for an hour or two first.
4. Use fresh whole cow’s milk while they recover. Switch to plant milk once they ferment normally again.
5. Change the milk every 24 hours, even if the batch looks thin. Throw away a batch that is still like milk at 36 hours.

Going away? Read How to put the grains on pause before you leave.

How to keep kefir grains strong

• Room temperature: keep grains below 35°C. Ferment them in a jar at room temperature, out of the sun, and away from yogurt makers, rice cookers, ovens, microwaves and hot cars.
• Milk rinses and dry tools: rinse grains with milk, and dry every jar, strainer and spoon completely. Wash jars with plain dish soap and rinse it off well.
• Regular feeding: grains feed on lactose, the sugar in cow’s milk. Ordinary whole milk suits them best. Change it regularly to keep them strong.
• Cow’s milk days: grains can ferment soy milk, and they grow best in cow’s milk. After about six days of plant milk, give them a day of fresh cow’s milk. More in Fermenting kefir with soy milk and other plant milks.
• Fresh milk: grains usually ferment fresh pasteurised whole milk better than long-life (UHT) milk. See Milk matters.

When to start fresh

• Mould: any pink, red, orange, green, blue, grey or black patch or fuzz on the grains or the milk. Throw away all of it, including the parts that look clean.
• A rotten smell: throw everything away when it smells rotten instead of sour.
• Insects: pour away the kefir if an insect gets into the jar. With a cockroach, throw the grains away too.
• Tired for too long: start fresh after about a month without growth and with weak fermentation, or after about five failed batches in a row with less milk and the right temperature.

Then start again with fresh grains, a clean dry jar and the steps in our kefir-making guide.

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Frequently asked questions

Live kefir grainsSee them