Hydrogen is soluble in water. Under standard conditions, the solubility of hydrogen is 1.83%, which means that at most 1.83 ml of hydrogen can be dissolved per 100 ml of water. The solubility is indeed relatively small, but in biology, the solubility is about 0.8mM, which means that about 1.6mg of hydrogen is dissolved per 1 liter of water. In the field of medical biology, both mM and mg are relatively large units. Many of the drugs we take are mostly in this order of magnitude. If we have doubts about the solubility of hydrogen, we can compare another important gas, the solubility of oxygen. The solubility of oxygen under standard conditions is 2.4%, which is very close to the solubility of hydrogen 1.83%. If oxygen is considered insoluble or poorly soluble in water, then fish living in water cannot breathe oxygen.


