Does deep breathing give you more oxygen? What actually happens in your blood

Your blood is already nearly full

Oxygen travels in your blood mostly on a protein called hemoglobin. In healthy people breathing normally at sea level, 96 to 98 percent of its spots are taken.¹ There isn’t much room left at the top.

On top of that, oxygen binding has a quirk: above about 90 percent, the curve flattens out. If you breathe faster or deeper, the oxygen pressure in your blood rises a little, but saturation barely moves.¹ And it can’t go past 100 percent anyway.

1. Calm breathing: your blood is 96 to 98 percent saturated with oxygen.
2. Deeper, faster breathing: saturation barely rises, and it can’t go past 100 percent anyway.
3. Instead, you breathe off more carbon dioxide, and its level in your blood drops.
4. Less carbon dioxide makes the blood vessels in your brain narrower. Dizziness and tingling can follow.

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What deep breathing actually changes

When you breathe more than your body needs, you mainly blow off more carbon dioxide. Many beginners do this mildly even during slow, paced breathing: in a study of 46 college students, the carbon dioxide level in exhaled air dropped by about 5 mmHg on average. With an instruction not to breathe excessively deep, just naturally, it dropped by under 3.²

Carbon dioxide isn’t just waste you need to get rid of. Among other things, it controls how wide the blood vessels in your brain are. When it drops sharply, they constrict: with very strong overbreathing, blood flow to the brain can fall by 40 to 50 percent.³ Gentle breathing exercises don’t get anywhere near that. But the direction explains why breathing too deeply can make you dizzy rather than more alert.

One more thing, simplified: carbon dioxide helps hemoglobin release its oxygen where it’s needed. This Bohr effect means blood lets go more easily in working tissue that’s rich in carbon dioxide, and picks up oxygen more easily in the lungs.¹ How much overbreathing during breathing exercises affects this hasn’t been measured.

What about “18% more oxygen” from nose breathing?

That number shows up in books and videos about nasal breathing. A fact check by McGill University tracked it down.⁴ It comes from a small 1996 study: in six patients on mechanical ventilation in intensive care, the oxygen pressure in their blood rose by 18 percent when air from their own nose was fed into the ventilator. In healthy people, only a value measured through the skin was recorded; in 6 of 8 people, it was 10 percent higher with nasal breathing.⁵ The study didn’t measure how saturated healthy people’s blood was.

What is true: your sinuses produce a gas called nitric oxide, and it reaches your lungs mainly when you breathe through your nose.⁵ That this gives healthy people at rest noticeably more oxygen in their blood hasn’t been shown. What nasal breathing can do is covered in the article on nasal breathing.

Does Wim Hof breathing oxygenate your blood?

In the best-known study, twelve trained men breathed with the method: hard and fast, followed by long breath holds. The average oxygen pressure in their blood stayed practically the same. But at the end of each hold, oxygen saturation dropped to around 50 percent for about ten seconds, and blowing off carbon dioxide made their blood strongly alkaline.⁶ That’s not more oxygen. What this means for safety is in the article on breathwork and Wim Hof.

Why fast breathing before diving is dangerous

This is where carbon dioxide really matters. If you hyperventilate before going underwater, you lower it. The urge to breathe kicks in later while oxygen keeps dropping, and you can black out underwater without warning. In a CDC report, all four people who died this way had deliberately hyperventilated first, even though they were very strong swimmers.⁷

Common questions

Are there breathing exercises to get more oxygen into your blood?

For healthy people at rest, they add barely anything: your blood is already 96 to 98 percent saturated.¹ Breathing exercises can still feel good, just for other reasons.

Can you breathe too deeply?

Yes. Carbon dioxide drops, and dizziness or tingling can follow. What helped in one study: not breathing excessively deep, just naturally.² More in When breathing exercises make you anxious or dizzy.

Does deep breathing give you more energy?

There’s no evidence for that. With overbreathing, the physiology points the other way: blood vessels in the brain get narrower.³

Does nose breathing give you 18% more oxygen?

That figure comes from measurements in six patients on ventilators. For healthy people at rest, it hasn’t been shown.^{5, 4}