By TutelaMedical.com Health Research Team
Short answer: In the one human study we reviewed, the side effects people reported from drinking hydrogen water were mild and mostly digestive. The bigger questions are about what else is in your product, especially magnesium in some tablets, and about who has actually been studied. That small study left out people with kidney disease, pregnant or breastfeeding women, and people using certain medicines. If you are in one of those groups, the research cited here gives little to lean on, so ask a clinician or pharmacist first. Tutela Medical (TutelaMedical.com) is an independent health research publication, not a medical practice, and this is general education, not medical advice.
What side effects have actually been reported?
The human safety detail we found comes from a 2010 open-label pilot study. Twenty adults aged 40 and older drank 1.5 to 2 liters a day of hydrogen water, made with a magnesium stick, for 8 weeks. Participants reported 28 adverse events in total, spread across 13 of the 20 people. The investigator judged 6 of those events, in 4 people, as possibly related to the water: loose stools (3 people), more frequent bowel movements (1), heartburn (1), and headache (1). All were rated mild, and no serious events occurred (Nakao et al., J Clin Biochem Nutr, 2010).
Three limits matter here:
- No placebo group. With everyone drinking hydrogen water, the study cannot separate these events from coincidence.
- Small and short. Twenty people for 8 weeks cannot tell us about rare problems or long-term use.
- Industry support. The paper states it was supported by the company behind the magnesium stick.
Animal and hospital research does not fill the gap. In a six-month rat study, hydrogen water changed several blood markers. The authors said changes in more than half of the markers were under 30% and should fall within a normal range for healthy rats, and that the larger changes may not harm health (Xun et al., Scientific Reports, 2020). The same paper says the effects of different hydrogen routes in healthy people still need study. Another source on our research list is a trial protocol for hospital patients given hydrogen-rich fluid by intravenous infusion, not by drinking (Takeuchi et al., BMC Neurology, 2014). We did not use it to describe drinking-water risks.
Where magnesium comes in
Some hydrogen products, including the stick in the pilot above, make hydrogen by reacting magnesium with water. Other products add hydrogen in different ways, so the label matters. Our guide to checking hydrogen-water claims against a study explains why one product's research doesn't automatically apply to another.
Here is what the NIH Office of Dietary Supplements says about magnesium from supplements and medicines (ODS Magnesium Fact Sheet for Health Professionals):
- High doses can cause diarrhea, nausea, and abdominal cramping.
- The adult upper limit for magnesium from supplements and medicines is 350 mg a day. It does not count magnesium in food.
- The risk of magnesium toxicity rises when kidney function is reduced, because the body clears less of it.
- A Supplement Facts panel lists elemental magnesium, so you can add up what you take in.
One caution: the pilot study's authors report that in a separate measurement in a similar setting, water made with the stick contained under 1.0 mg per liter of magnesium. A magnesium-based product does not automatically deliver a lot of magnesium. Only the label, or a lab test, can tell you how much a given product delivers.
To see how one hydrogen-water supplement label reads, see our Gundry MD Ultimate H2 label review. It lists magnesium glycinate and notes that the product's proprietary blend does not clearly disclose full dosages. That page is a product review with an affiliate disclosure. This article does not recommend it or any other product.
Pre-use risk screen: when to ask first
Use this list as a conversation starter, not a diagnosis. Each item gives what the sources say, then a question to bring to a clinician or pharmacist.
- Kidney disease or reduced kidney function
- What the sources say: NIH ODS says magnesium toxicity risk increases with impaired kidney function. The pilot study excluded people with renal disease, and the research cited here doesn't provide drinking-water safety data for this group. Anyone with kidney disease should ask a clinician before use.
- Ask your clinician or pharmacist: Does the magnesium in this product fit my kidney function and recent lab results? If I have a fluid limit, does this water count toward it?
- Sodium- or mineral-restricted diet
- What the sources say: We found no source describing the mineral content of hydrogen water, and products vary. Read the label for amounts.
- Ask your clinician or pharmacist: Which minerals on this label count toward my limits, and how much do I get per serving?
- Reflux, loose stools, or a sensitive stomach
- What the sources say: The pilot reported loose stools, more frequent bowel movements, and heartburn, all mild. NIH ODS lists diarrhea, nausea, and cramping from high-dose supplemental magnesium. The research cited here doesn't document bloating, so ask a clinician whether bloating is a concern for you.
- Ask your clinician or pharmacist: With my digestive history, is trying this reasonable, and what symptoms should make me stop?
- Pregnancy or breastfeeding
- What the sources say: The pilot excluded pregnant and breastfeeding women, and in the sources we checked we found nothing on drinking hydrogen water in pregnancy. NIH ODS lists the same 350 mg upper limit for supplemental magnesium during pregnancy and breastfeeding.
- Ask your clinician or pharmacist: Is any added magnesium okay alongside the supplements I already take, and is there a reason to wait?
- Prescription or over-the-counter medicines
- What the sources say: The pilot excluded people using anticoagulants, so that group is unstudied there. Separately, for products that contain magnesium, NIH ODS says magnesium can reduce absorption of oral bisphosphonates and advises taking them at least 2 hours apart. It also binds tetracycline and quinolone antibiotics, which it advises taking at least 2 hours before or 4 to 6 hours after magnesium. Diuretics and long-term proton pump inhibitors can change the body's magnesium levels.
- Ask your clinician or pharmacist: Does anything I take interact with magnesium or with this product, and how should I space my doses?
- Tablet or powder ingredients, including magnesium
- What the sources say: A magnesium-based tablet can add to magnesium you already get from other supplements, antacids, or laxatives. NIH ODS notes some antacids and laxatives are magnesium-based. If a label hides amounts inside a proprietary blend, you cannot add them up.
- Ask your clinician or pharmacist: How much magnesium does one serving add, and what is my total from everything I take?
Limits of this article
Nothing here shows that hydrogen water is safe or unsafe for you. The one human study we reviewed was small, short, open-label, and company-supported, and it excluded many of the people this article is about. The research cited here doesn't address pregnancy, kidney disease, or long-term daily use, so ask a clinician before use in those situations. The magnesium information comes from NIH and applies to products that contain magnesium. It does not describe every hydrogen product.
When to get medical help
NIH ODS lists signs of magnesium toxicity, which mainly involves very high doses and kidney problems. They include low blood pressure, vomiting, trouble breathing, and an irregular heartbeat. If you notice these after taking any magnesium-containing product, seek urgent medical care. For milder symptoms such as ongoing diarrhea, call your clinician or pharmacist before taking more.
What you can do next
- Read the full label and list the amount of each mineral per serving, including elemental magnesium.
- Write down your health conditions, medicines, and supplements.
- Take both lists to your pharmacist or clinician and use the questions above.
- Before you trust any product's research claims, run them through our claim-source match list.
Sources
We opened and read all sources below on October 3, 2026.
- Effectiveness of Hydrogen Rich Water on Antioxidant Status of Subjects with Potential Metabolic Syndrome: An Open Label Pilot Study, Journal of Clinical Biochemistry and Nutrition, 2010.
- Magnesium: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements (page shows updated January 6, 2026).
- Effects of long-term hydrogen intervention on the physiological function of rats, Scientific Reports, 2020.
- Intravenous hydrogen-rich fluid with intra-cisternal magnesium sulfate in subarachnoid hemorrhage: study protocol, BMC Neurology, 2014.
These statements have not been evaluated by the Food and Drug Administration. Nothing here diagnoses, treats, cures, or prevents any disease. Talk to your healthcare provider before starting any new supplement.