Molecular hydrogen is gaining popularity across the globe. Unfortunately, many people misunderstand molecular hydrogen, so there are several questions regarding many of the subjects surrounding this gas.
This page answers the questions we receive most often and provides evidence-based explanations. Because many of these topics have dedicated articles, we’ve also included links to more in-depth resources throughout when applicable.
If you are new to molecular hydrogen? We recommend starting with The Complete Guide to Molecular Hydrogen Therapy, which provides a comprehensive overview of the science, mechanisms, administration methods, safety, and current research.
Getting Started
Molecular hydrogen (H2) is the simplest and smallest molecule in the universe. It consists of two hydrogen atoms chemically bonded together to form a neutral, colorless, odorless, and tasteless gas.
Although hydrogen is the most abundant element in the universe, molecular hydrogen (H2) is distinct from the hydrogen atoms that are chemically bound within other molecules, such as water (H2O) or carbohydrates. These forms of hydrogen have very different chemical properties and biological roles. Throughout this website, the term molecular hydrogen refers specifically to hydrogen gas (H2).
Over the past two decades, molecular hydrogen has become the subject of thousands of scientific publications investigating its potential biological effects. Research suggests that hydrogen may influence cellular signaling, oxidative stress, inflammation, and other processes involved in maintaining cellular homeostasis. While many findings are promising, research is ongoing, and the strength of evidence varies.
Molecular hydrogen can be administered in several ways, including drinking hydrogen-rich water, inhaling hydrogen gas, injecting hydrogen-rich saline, or stimulating hydrogen production by gut bacteria through the fermentation of dietary fiber.
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Although these terms all contain the word “hydrogen,” they refer to three very different things.
- Hydrogen gas (H2) is two hydrogen atoms bonded together. This is the form of hydrogen that has been studied for its potential therapeutic effects and is the form referred to throughout this website.
- Hydrogen ions (H+) are single hydrogen atoms that have lost their electron, leaving only a positively charged proton. Hydrogen ions determine the pH of a solution and are responsible for acidity.
- Hydrogen atoms (H) are individual hydrogen atoms that are typically chemically bound within other molecules, such as water (H2O), carbohydrates, fats, and proteins. These hydrogen atoms have completely different chemical properties than molecular hydrogen gas.
Although all three contain hydrogen, they behave very differently in chemistry and biology. Throughout this website, when we refer to molecular hydrogen, hydrogen gas, or hydrogen water, we are referring specifically to molecular hydrogen (H2).
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Hydrogen water or hydrogen-rich water (also called hydrogen-enriched water) simply means normal water (H2O) that contains dissolved molecular hydrogen gas (H2).
For example, there are carbonated waters and other beverages that contain dissolved carbon dioxide gas (CO2), and there are oxygenated waters that contain dissolved oxygen gas (O2). Similarly, hydrogen water is simply water that contains dissolved molecular hydrogen gas.
One way to think about it is this: you can make hydrogen water by taking a tank of hydrogen gas (similar to tanks of helium used to fill balloons or oxygen tanks used in hospitals) and bubbling the hydrogen gas into a glass of water. While this is one method of producing hydrogen-rich water, there are several others, including electrolysis and hydrogen-generating tablets. Regardless of how it is produced, hydrogen water is simply water containing dissolved molecular hydrogen gas.
It is important to note that the hydrogen gas is not chemically bonded to the water molecule. Instead, it is physically dissolved in the water and gradually escapes into the air over time. For this reason, hydrogen-rich water is generally best consumed soon after it is produced or from containers designed to minimize hydrogen loss.
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It is true that hydrogen is not very water soluble as it is a neutral, non-polar molecule with a solubility of 1.6 mg/L, which is relatively low. But when we consider that molecular hydrogen is the lightest molecule in the universe, we really need to compare the number of molecules as opposed to the number of grams. For example, if a single molecule weighed 2 mg (which is impossible, but used as an example), then having just one of those molecules in a liter of water would give you 2 mg/L, but there would only be one molecule. For reference, vitamin C (176.2 g/mole) weighs 88 times more than hydrogen gas (2 g/mole). Therefore, hydrogen water at a concentration of 1.6 mg/L would have more “therapeutic” molecules than 100 mg of vitamin C, as there are more total molecules in 1.6 mg of hydrogen compared 100 mg of vitamin C. That is, 0.8 mmoles of H2 vs. about 0.6 mmoles of vitamin C. But more importantly, hundreds of scientific studies clearly show that these concentrations of hydrogen are effective.
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Yes, it does immediately start coming out of the water, but it doesn’t just vanish immediately. Depending on the surface area, agitation, etc., the hydrogen gas can stay in the water for a few hours or longer before it drops below a therapeutic level. This is much like carbonated water or soda that contains carbon dioxide gas (CO2), but because it does leave, it is best to drink the water promptly before it goes “flat”. (see this article also).
Learn more:
- Dissolved Hydrogen Versus Undissolved Hydrogen
- Concentration and Solubility of H2
- Hydrogen Water: What Is the Hype?
- How Should Hydrogen-Rich Water Be Stored?
That is the same question scientists are asking and is still under investigation. However, the animal and human studies generally provide about 0.5 to 1.6 mg or more of H2 per day for hydrogen water, and these doses show statistically significant benefits. So, if your water has a concentration of 1 mg/L (equivalent to 1 ppm, parts per million), then two liters will give you 2 mg of H2. Although the effective concentration for some people and some diseases may be lower and/or higher, these doses are simply what have been seen to exert benefits. (see this article also). For inhalation, it is recommended to use greater than 1% FiH2, but less than 4% to stay below the lower flammability limit.
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Maybe, maybe not…. There is obviously a minimum required amount needed to offer any health benefits, which may vary from person to person. Importantly, it appears that you cannot get too much hydrogen, as it doesn’t build up in your system—you just exhale it out. In many cases, at least for hydrogen water, there is a clear dose-dependent effect, meaning the more hydrogen the better or greater the effect. There are also many anecdotal reports that suggest that consuming more hydrogen may offer even more benefits. But more research needs to be done in this area. In other cases, for inhalation, lower FiH2 sometimes have greater effects than higher FiH2, such as in the 2007 Nature Medicine article where 2% had greater benefits than the 4% inhalation. However, this doesn’t always seem to be the case so between 1-4% is generally the recommended range.
Learn more:
- What Molecular Hydrogen Does Not Appear to Do (Yet)
- Can You Consume Too Much Molecular Hydrogen?
- Calculating the Dose of H2
- Concentration vs. Flow vs. Duration
