Moon breath (chandra bhedana)

How to do it

1. Sit tall with your shoulders relaxed. If you're doing it in bed, prop your back against a pillow.
2. Bring your right hand to your face: thumb beside the right nostril, ring finger beside the left. If your arm gets tired, rest the elbow in your other hand.
3. Close the right nostril with your thumb and breathe in through the left for 4 seconds.
4. Close the left nostril with your ring finger, release the thumb and breathe out through the right for 6 seconds.
5. Close the right side again and open the left for the next inhale. The air always comes in on the left and leaves on the right; there's no return trip on the other side.
6. Keep going for 5 minutes, which is 30 cycles of 10 seconds.
7. After the last exhale, lower your hand and breathe through both nostrils for a moment before you move or lie down.

What it is

It's a one-way breath: in through the left nostril and out through the right, cycle after cycle. The 6-second exhale is longer than the 4-second inhale. At that pace you take six breaths a minute.

It's easy to mix up with its neighbors. In alternate nostril breathing (nadi shodhana) the air comes back through the opposite side, so both sides get the same. In the sun breath (surya bhedana) the route is reversed: the air comes in on the right. And there's an even simpler form, which some studies call chandra nadi, where the air goes in and out on the left.

Where it comes from

Chandra is the moon in Sanskrit. The Hatha Yoga Pradipika, the 15th-century hatha yoga manual attributed to Svatmarama, uses that word for the left nostril and calls the right one surya, the sun. It also names the two channels tradition ties to each side: ida on the left and pingala on the right. That's how yoga describes the body, not anatomy.

What the text doesn't have is a breath called chandra bhedana. Its list of eight pranayamas opens with surya bhedana, the sun breath, and includes no moon version. The moon breath is taught today as the sun breath's mirror image, and it appears under that name in studies done in India in recent years. We couldn't confirm who first named it or in which text, so we don't say.

What people use it for

Yoga schools today present it as the breath that quiets, the counterpart to the sun breath, which is presented as the one that activates. That's why people who practice it tend to do it at dusk, before bed or after a stretch of heavy stimulation.

Tradition aside, it has two practical traits. Breathing through one nostril slows the air down without any effort on your part, and the hand at your face gives your attention a simple job. Some people find the gesture distracting in bed. If that's you, do it sitting up and lie down afterward.

What studies say

There are studies, nearly all small and done in India, and their results don't always agree. None used exactly these counts.

In 2008, a study of 21 men who already practiced yoga compared 30 minutes of left nostril, right nostril and alternate nostril breathing. After the left side, systolic and mean blood pressure went down; after the right side, blood pressure went up. In 2014, another study with 20 yoga-trained people measured nine rounds of several techniques, chandra bhedana among them: the ones that started on the left lowered heart rate and blood pressure.

Other results cool the idea of two opposite sides. A 2005 study of 40 students, half in each group, saw no sharp difference between breathing through the left and through the right: both groups shifted in the same direction.

On sleep we found a single study, from 2022, in which medical students practiced left nostril breathing for four weeks and reported better sleep on a questionnaire. It measures what people say, not their sleep. The evidence is limited and doesn't support promising an effect.

What it feels like and what to notice

The first thing almost everyone notices is that one side of the nose is more open than the other. That's normal, and it's called the nasal cycle. The German physician Richard Kayser described it in 1895: the two nostrils take turns letting more air through, in cycles that average about two and a half hours. If the left is the tighter one today, the inhale will feel narrow. Don't pull at the air: take whatever comes in during the 4 seconds.

After a few minutes the air feels cool in the left nostril and the breath evens out. Signs to stop: shortness of breath, dizziness, or a sense that you're forcing your nose. Lower your hand and breathe through both sides.

Variations

• Easier: count 3 seconds in and 5 out on your own until 4 and 6 feel comfortable.
• Longer: go up to 10 minutes at the same counts. There's no need to stretch the phases.
• Left side only (chandra nadi): breathe in and out through the left nostril, keeping the right closed the whole time. That's the form several studies use.
• Traditional, with a hold: yoga schools add a pause with the lungs full between the inhale and the exhale. That's a more advanced practice, learned with a teacher, and it isn't part of this guide.

Common mistakes

• Pinching the nose. A light touch that blocks the air is enough; you're not pushing on the septum.
• Sniffing hard when the left nostril is half blocked. It's noisy, it's tiring and it doesn't help.
• Switching sides without noticing and ending up doing alternate nostril breathing. Here the air always comes in on the left.
• Tilting your head toward your hand or hiking up your right shoulder.
• Cutting the exhale short. The 6 seconds out are the slow half of the cycle: spread the air across them.

How often and how long

Five minutes at the end of the day is enough to start. Studies used very different amounts, from nine rounds to half an hour, so there's no dose we can recommend with any backing.

Before you start

• If your nose is badly blocked by a cold or allergies, save it for another day. Don't force air through a closed nostril.
• If you feel dizzy or short of breath, lower your hand and breathe normally through both nostrils.
• If you have low blood pressure, a heart or lung condition, or you're pregnant, check with your care provider first.
• Don't do it while driving.