Kefir is a fermented milk, a bit like yogurt, that contains up to 30 different species of probiotic (health-benefitting) bacteria and yeasts. It’s been an essential part of the diet in Eastern Europe for the last 2000 years, and gradually it has made its way to the UK.


A rich source of bioactive peptides, vitamins, minerals and enzymes, it’s been studied by scientists for over a hundred years. Read up on the health benefits of kefir and more information on probiotics.

Kefir is easy to make safely at home, with minimal kit requirements, so it’s definitely worth adding to your family’s diet. It has a reputation for having a strong, sour flavour that isn’t to everyone’s taste, but it’s surprisingly easy to control the process so it’s delicious and mild. Despite the detailed instructions that follow, making your own kefir can take as little as five minutes per batch, from start to finish.

Where to find kefir grains

Kefir grains on spoon

You can’t make kefir without kefir grains. The 'grains' are actually bacteria and yeast that look like tiny cauliflower florets, bound together in a kefiran polysaccharide matrix. If you know someone who already makes kefir, ask them if you can have some – as little as half a teaspoon will be enough to make your own. Alternatively, fresh grains can be purchased online. If they arrive in the post, they may need a little re-invigorating after their journey; put them in a small jar and cover with whole milk – you won’t need more than 100ml. Cover and leave on the side for 12-48 hours until the milk has set (it varies depending upon milk used and temperature). When it does, you’re good to go and can scale up.

What is fermentation?

In food terms, it’s a process where we provide microbes with an energy source (here we are using milk), and they use it to grow, making end products that are useful to us – in this case, lactic acid that sours the milk and makes kefir. The microbes also produce carbon dioxide which can make kefir fizzy. Other examples are our simple sauerkraut, quick kimchi, kombucha and yogurt. Check out our beginner's guide to fermented foods for more essential info.

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Equipment you will need

  • ½ teaspoon of kefir grains (see below for where to get them and how to ensure they’re ready to use)
  • 1 pint of fresh milk (organic whole milk for best results)
  • 500 ml clip-top jar with gasket for fermenting (or jar, cover and rubber band)
  • a spoon
  • a sieve and jug/bowl and storage bottle or a straining funnel and wide necked bottle
  • optional – a slice of lemon/drop of lemon oil

If you're looking to upgrade your kitchen kit, here are some of our tried, tested and top-rated favourites that would come in handy for making kefir.

Choosing a method for making kefir

People usually use glass vessels because then you can see what is going on. For a stronger flavour, use an open system – cover a large jar with a cloth cap or paper towel and rubber band and ensure there are several inches of air above the milk. The closed system uses a clip top jar with a rubber gasket to keep oxygen out. The microbes in the kefir grains are able to grow well with just a little oxygen present. These conditions will also ensure that Lactobacilli grow better than the other types of microbes, reducing yeasty flavours and fizz (though the amount of grains used is also very important).

To make a mild tasting kefir, use 5-10g grains per litre of milk. Anything above this will give a stronger tasting kefir that will ferment more rapidly. Ensure your equipment is dishwasher clean, or has been washed in hot soapy water, and rinsed well before you start.

Kefir recipe


  1. Put ½ tsp kefir grains in the jar.
  2. Add a pint of milk, leaving about 2cm head room if using a clip top jar, or at least 5cm for a cloth-covered jar.
  3. Leave on the worktop for 18-24 hours to ferment. It’s turned to kefir when the milk has thickened. It may have set and separated, with pockets of whey forming – this is quite normal.
  4. When set, if you can’t strain it straight away, put it in the fridge to stop it fermenting further, as the flavour can get quite strong – you can strain it anytime over the next 48 hours.
  5. Strain the kefir through the sieve or straining funnel into your jug or bottle. The grains are quite robust and will withstand gentle stirring.
  6. You can drink it straight away, flavour and refrigerate it (a slice of lemon peel or a drop of lemon oil add a delicious fresh taste), or leave it at room temperature for a few hours to make it taste stronger.

Rinse out the jar, put the grains back in (don’t wash them, there’s no need), fill it up with milk again and leave at room temperature to make some more.

How do I know if it’s ready?

The grain/milk ratio and the temperature both affect how quickly milk will become kefir. Put the jar somewhere (out of direct sunlight) where you can keep an eye on it. Try to catch it when just set for a milder flavour. If it separates into curds and whey don’t worry as it can be easily mixed back together. With practice you’ll be able to time it just right. It’s harder to tell with skimmed milk which gives a much softer set. Poke with a spoon if you aren’t sure if it’s thickened, and smell it – if it smells slightly yogurty or mildly cheesy, it’s done.

At first it might take up to 48 hours for the milk to thicken. You can tell it’s ready as the milk will set, just like yogurt. Pockets of whey might appear; don’t worry this is normal and they will mix in during straining.

How should it taste?

The kefir should taste yogurty and tangy, but it usually lacks the slightly sweet aftertaste of yogurt. If you’ve tasted shop bought kefir, you might be in for a bit of a surprise at first, but you really can learn to love the homemade variety. If you choose to use lots of grains and grow in an open system it can taste fizzy and yeasty. If you use a few grains and a low-oxygen environment it can taste fresh and mild.

How should kefir be stored and how long does it keep?

Once strained, keep the kefir in the fridge. This will slow down the fermentation by the microbes. It should remain pleasantly useable for 7-10 days. It will not ‘go off’ as such, as it is already fermented, but the flavour might become rather strong. You can make a larger batch once a week if you don't want to make it daily. Half a teaspoon of grains will even convert a much larger volume of milk to kefir – add a little kefir in with the grains to get things started more quickly if you’re scaling up.

In between batches, keep the grains covered in a little jar of milk on the worktop for up to a week or up to three weeks in the fridge. Change the milk if you’re still not using them or they will starve.

Kefir grains are living organisms, and will gradually grow (not in all milk alternatives, though). When they’ve doubled in size, which might take two or three weeks with daily making, take out half of them and give them to a friend, or freeze them. If you don’t remove the excess you will notice the flavour of the kefir changing.

What type of milk should I use?

Milk being poured into jars

Use whole organic milk (usually blue top) for the best tasting, most nutritious kefir as the grassy diet for organic cows makes milk of superior nutritional quality. Any fresh animal milk works, from skimmed to full fat Jersey, goat, cow or even UHT. The higher the milk’s fat content, the thicker the kefir.

Use fresh milk that is not on the turn; pasteurised milk contains some non-harmful bacteria that can grow at low temperatures and eventually change the flavour of the milk – this can make the kefir taste odd and make it curdle before it sets.

You can use homogenised or unhomogenised milk, but it’s worth noting that with high fat varieties of unhomogenised milk, sometimes the grains get stuck in the cream and the milk won’t set – you’ll need to stir or shake it a few times whilst it’s fermenting.

You can use raw (unpasteurised) milk. Sometimes people find that it’s hard to make kefir from unpasteurised milk because there are so many other bacteria already in the raw competing with the kefir bacteria for food. However, one could say that turning raw milk into kefir could be a safer way of consuming raw milk: there are so many ‘good’ microbes in the kefir grains that they can usually inhibit the growth of small numbers of pathogenic (harmful) bacteria that could be present in unpasteurised milk. Don’t use raw milk if you are pregnant.

Can I use metal utensils?

There is an urban myth that metal utensils should not be used with kefir grains, but short-term contact with a spoon or sieve is not a problem.

Contamination problems

These are rare. Kefir microbes do not welcome outsiders and it’s difficult for pathogens and moulds to take hold, especially in a closed jar. Also the acidic nature of kefir inhibits them. Sometimes in an open system, a dry powdery film can appear on the top. This is Kahm yeast and is not contamination as such, just natural yeasts in the kefir growing at the surface where they are happiest. You can continue to strain and consume this kefir.

Can everyone have kefir?

If you have a milk allergy you can substitute soya milk or coconut cream instead of dairy milk. Fermented foods can contain traces of histamine, which could be an issue if you have a severe histamine allergies.

If you are immunocompromised, have had recent gastric surgery, or have an underlying serious health condition please do check with your GP first before consuming. People with a dairy intolerance are often able to consume kefir as post-fermentation it has lower levels of lactose. IBS/IBD sufferers should try a couple of milliliters at first; it often helps with these conditions, but in some people may have the opposite effect. Trace amounts of alcohol could be present if a strong kefir is made.

How much kefir should you drink?

You will be introducing many new species to your gut, which can occasionally result in mild stomach upset symptoms, so the best advice is to start gradually, with a couple of teaspoons for the first day or two, doubling up over the next few days to about 150ml (though this is arbitrary; you can’t overdose as such).

Kefir with plant-based alternatives

You can make kefir with plant-based alternatives like coconut, soya or oat. Whichever you choose, it needs a high calorie content and about 3.5g sugar per 100ml, as this will be the microbe’s source of carbohydrate.

Soya milk makes excellent thick kefir, and the grains will usually grow in this medium. Tinned coconut cream is a better choice than coconut milk, and gives a thick, tangy, almost yogurty consistency; choose an organic brand as these have no additives. How well they will survive a non-dairy lifestyle entirely depends on your own kefir grains and the microbes they contain. If you notice that they are not making kefir, or not growing much, try refreshing them in some dairy milk for a few days. With the exception of soya milk, which contains many short-chain peptides, health benefits of other milk alternatives have not yet been investigated.

Our best kefir recipes

Kefir smoothie in glasses

Your strained kefir can go straight in the fridge if you want to have it plain. Refrigerating it for a few hours improves the flavour and also the texture as it tends to thicken a little. It might separate upon standing – don’t worry, shake or whisk with a fork to re-homogenise it. Try it in our kefir breakfast smoothie, or blend it with frozen banana for an instant ice cream. You can also try adding a pinch of salt and strain to make labneh (for a milder flavour, add some natural yogurt before straining). Make a creamy kefir dressing and pair with our charred veg & tuna niçoise salad.

More fermenting projects...

Beginner's guide to fermented foods
The health benefits of fermenting
The health benefits of kefir
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