Short answer
Yes. Milk kefir is fermented milk, and the small trace of alcohol that forms naturally in it cannot intoxicate, so it is halal in the Hanafi school and the others. A home brew left to ferment until it tastes or acts like alcohol is a different matter.
A fermented drink stays halal as long as it cannot intoxicate. Shop-bought and normally made milk kefir and water kefir are halal; a batch that has fermented to the point of intoxicating is haram.
The four schools agree on this.
Explanation
Kefir is made by adding kefir grains, a culture of bacteria and yeast, to milk and leaving it for about a day. The bacteria turn it sour, like yoghurt, and the yeast makes a little fizz and a trace of alcohol. Water kefir is the same idea using sugared water or juice. Both are widely sold in supermarkets as probiotic drinks.
The scholars do not ask whether a drink contains any alcohol molecule at all, since bread, ripe fruit and fresh juice contain traces too. They ask whether it intoxicates. The Prophet ﷺ himself drank nabidh, water with soaked dates or raisins, for up to three days and then had what was left poured away before it could turn. A drink that has begun to ferment is not forbidden until it can intoxicate. The four schools agree on this test.
- Shop kefir: halal. It is sold as a dairy product, not an alcoholic drink.
- Home-made kefir: halal when made the normal way. Do not leave it fermenting for many days, and pour away a batch that smells or tastes boozy.
- Flavoured kefir: check for gelatin or other added ingredients.
- Kefir cheese and kefir yoghurt: halal on the same basis.
The same test answers kombucha and non-alcoholic beer. Other cultured dairy, such as yoghurt, buttermilk and ayran, is halal too.
The evidence
Quran, Surah An-Nahl 16:66
وَإِنَّ لَكُمْ فِى ٱلْأَنْعَٰمِ لَعِبْرَةًۭ ۖ نُّسْقِيكُم مِّمَّا فِى بُطُونِهِۦ مِنۢ بَيْنِ فَرْثٍۢ وَدَمٍۢ لَّبَنًا خَالِصًۭا سَآئِغًۭا لِّلشَّٰرِبِينَ ﴿٦٦﴾
And indeed, for you in grazing livestock is a lesson. We give you drink from what is in their bellies - between excretion and blood - pure milk, palatable to drinkers.
Milk is a lawful blessing; souring it does not change that.
Sahih Muslim 2004
Sahih... فإذا كان مساء الثالثة شربه وسقاه ...
"On the evening of the third day he would drink it and give it to others."
A drink that has started to ferment is lawful until it can intoxicate.
Sahih Muslim 2003
Sahih... كل مسكر خمر وكل مسكر حرام ...
"Every intoxicant is khamr, and every intoxicant is haram."
The test is whether the drink intoxicates.
Where the ruling is recorded
- al-Hidaya, Kitab al-Ashriba. Drinks are forbidden when they become intoxicating.
- Takmilat Fath al-Mulhim (Mufti Taqi Usmani), Kitab al-Ashribah. Commentary on the hadith of nabidh and the line at which a drink becomes forbidden.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.