Hydrogen Studies is funded by Echo Technologies LLC, which sells hydrogen water products. Echo doesn't decide which studies we cover or how we describe them — see our editorial policy.
Short answer: Hydrogen tablets are magnesium tablets that fizz hydrogen gas into a glass of water, and the magnesium stays in the drink. In the few human trials that used them, reported side effects were uncommon and mostly digestive, such as diarrhea or stomach pain. In the largest trial (675 people), these were about as common with placebo tablets, which also contained magnesium. The more practical issue is magnesium: each milligram of hydrogen takes about 12 mg of magnesium to make, so several tablets a day can approach the 350 mg adult limit for supplemental magnesium. Evidence of benefit is limited and mixed, and no tablet trial we found lasted longer than 24 weeks.
What are hydrogen tablets, and how do they make hydrogen?
Hydrogen tablets typically contain magnesium metal plus organic acids. Dropped into water, the magnesium reacts and releases hydrogen gas (H₂), which partly dissolves into the drink.
The basic reaction is Mg + 2H₂O → Mg(OH)₂ + H₂. One tablet described in a 2019 trial contained 80 mg of metallic magnesium plus malic and tartaric acids, which neutralize the magnesium hydroxide and speed up the reaction [1]. With the acids, the reaction is written Mg + 2H⁺ → Mg²⁺ + H₂ [2]. Either way, one magnesium atom is used for every hydrogen molecule released.
For how tablets compare with other ways of making hydrogen water, see what is hydrogen water?
How do brands like H2 Tabs and Vital Reaction compare?
We don't test or rank tablet brands. Hydrogen Studies has no hydrogen-measurement lab, and none of the trials on this page compared commercial brands with each other. Tablets sold under names people search for, such as H2 Tabs, Drink HRW, Vital Reaction and PrimeCell H2, are generally magnesium-based and work the way described above. Check each product's ingredient list to confirm.
What you can compare yourself, from the label and the maker's documentation:
- Magnesium per tablet. This decides how many tablets a day fit under the 350 mg limit (see the table below).
- The hydrogen claim, and how it was measured. Look for a concentration (mg/L or ppm) in a stated volume of water, measured by a named method or an independent lab. "High ppm" on its own tells you nothing.
- Directions. How much water per tablet, and how soon to drink it. Hydrogen escapes from an open glass within minutes [1].
- Other ingredients, such as acids, flavors, sweeteners or added minerals.
- Cost per day, at the number of tablets you would actually take.
Why there are no brand reviews on this site. We used to publish reviews of individual tablet brands. They described hydrogen measurements we can't document, so on 28 September 2026 we removed them and pointed them to this page. Hydrogen Studies is also funded by a company that sells hydrogen products, which is another reason we don't rate other companies' products.
How much magnesium is in a hydrogen tablet drink?
All of the tablet's magnesium ends up in your glass, even though much of the hydrogen bubbles away. Check the label: one tablet described in a trial contained 80 mg [1].
Our calculation. Magnesium weighs about 24.3 g per mole and hydrogen gas about 2.0 g per mole, so generating 1 mg of hydrogen uses about 12 mg of magnesium. That matches the 2019 trial authors' own figure: 80 mg of magnesium could make at most about 6.6 mg of hydrogen [1]. Going the other way:
- 5 mg of hydrogen ≈ 60 mg of magnesium
- 10 mg of hydrogen ≈ 121 mg of magnesium
- 15 mg of hydrogen ≈ 181 mg of magnesium
These are minimums, because the magnesium is used up by all the hydrogen a tablet generates, not just the part that stays dissolved. By the same math, the daily hydrogen amounts reported in tablet trials imply roughly 100 mg of magnesium a day at about 8 mg of H₂ [2], at least 134 mg at more than 5.5 millimoles [3], and at least 243 mg at more than 10 millimoles [8].
How that compares with the limit. For adults, the Tolerable Upper Intake Level (UL) for magnesium from supplements and medicines is 350 mg a day. It doesn't include magnesium in food [9]. Diarrhea was the effect used to set that limit in 1997 [10].
| Tablets a day | Magnesium, if each tablet has 80 mg* | Share of the 350 mg adult limit |
|---|---|---|
| 1 | 80 mg | 23% |
| 2 | 160 mg | 46% |
| 3 | 240 mg | 69% |
| 4 | 320 mg | 91% |
| 5 | 400 mg | 114% (over) |
*80 mg is the only tablet magnesium content we found in a published trial [1]. Products differ, so use your label's number.
Trials used 2 to 5 tablets a day (see below). Magnesium from other supplements, antacids or laxatives adds to the same total. Some magnesium researchers argue the 350 mg limit is too cautious [10], but it's the current official limit [9].
What side effects have hydrogen tablet trials reported?
Few, and mostly digestive. The larger caveat is how little these trials can tell us: most were small, and several only noted that the product was "well tolerated."
| Study | Who took part | Tablets a day (water per tablet) | Hydrogen, as reported | Length | Placebo | Side effects reported | Main result |
|---|---|---|---|---|---|---|---|
| LeBaron 2020 [3] | 60 adults with metabolic syndrome | 3 (250 mL) | >5.5 mmol/day | 24 wk | Look-alike drink | All finished; no ill effects reported | Cholesterol, glucose, HbA1c and inflammation markers improved vs placebo |
| Kura 2022 [4] and Sumbalová 2023 [5] (same trial) | 30 adults with fatty liver disease | 3 (330 mL) | >4 mg/L | 8 wk | Tablets with magnesium carbonate | All finished "without adverse events" | Mostly non-significant trends; some lab markers changed |
| Gaboreau 2024 [6] | 675 outpatients with COVID-19 | 2 (250 mL) | Not stated | 21 days | Same tablet, magnesium carbonate instead of magnesium metal | Adverse events 27.0% vs 26.2%; diarrhea or abdominal pain 44 vs 48 people | No difference in clinical worsening |
| Ogannisyan 2025 [2] | 22 female elite athletes | 2 (500 mL) | ≈8 mg/day | 28 days | Magnesium oxide tablets | None attributed to hydrogen water | Body composition and strength changed from baseline in the hydrogen group |
| Singh 2023 [8] | 10 adults with chronic lung disease | 5 (200–300 mL) | >10 mmol/day (estimated) | 4 wk | None (no control group) | Not reported | Oxygen saturation higher than at baseline |
| Todorovic 2025 [7]† | 36 adults with obesity | Format not stated† | 15 mg/day (1.0 L) | 8 wk | Tap water | No severe adverse effects; one person had more frequent bowel movements | Cravings, sleep quality, cholesterol and GLP-1 improved vs control |
†The drinks were supplied by a company that makes hydrogen tablets, but the paper doesn't say how they were made.
The largest trial. In the 675-person COVID-19 trial, 44 people taking hydrogen tablets and 48 taking placebo tablets had expected side effects such as diarrhea or abdominal pain. Eight in each group vomited, and five in each group had allergic-type reactions. A few people in the hydrogen group noticed a sensation of metal rubbing on their dentures. About 4–5% in each group stopped because of an adverse event [6]. Everyone in this trial had COVID-19 and everyone swallowed magnesium, so these numbers can't separate the tablets' effects from the illness or from magnesium.
A correction. An earlier version of this page said the 2025 obesity trial found "no adverse effects." That was incomplete: the abstract reports no severe adverse effects, and the results section describes one person in the hydrogen group with more frequent bowel movements [7]. That trial asked specifically about stomach upset, bloating, constipation, diarrhea, nausea and vomiting [7].
Why the placebo matters. In at least four tablet trials, the placebo tablets also contained magnesium [1, 2, 4, 6]. That design isolates the hydrogen, but it means none of these trials measured side effects of tablets against a no-magnesium comparison.
For side effects of hydrogen water in general, including non-tablet trials, see hydrogen water side effects.
Who should be cautious with hydrogen tablets?
Mainly people who need to watch their magnesium: those with reduced kidney function, those taking certain medicines, and children.
- Kidney disease. The kidneys clear excess magnesium, and the risk of magnesium toxicity rises when they can't [9]. Ask your nephrologist before using tablets; see is hydrogen water good for your kidneys?
- If you've been told to limit magnesium. Count tablet magnesium toward your limit.
- Some medicines. Magnesium can reduce absorption of oral bisphosphonates (for osteoporosis), so the NIH advises separating them by at least 2 hours. Tetracycline and quinolone antibiotics should be taken at least 2 hours before or 4–6 hours after a magnesium-containing supplement. Diuretics and long-term proton pump inhibitors affect magnesium levels [9]. Ask your pharmacist.
- Children. The supplemental magnesium limit is 65 mg a day at ages 1–3 and 110 mg at ages 4–8 [9]. An 80 mg tablet alone would exceed the limit for a toddler. None of the tablet trials we reviewed was designed to study children.
- Pregnancy. The adult limit of 350 mg also applies in pregnancy [9]. None of the tablet trials we reviewed reported results in pregnant women.
Very high magnesium intakes, typically above 5,000 mg a day from laxatives or antacids, have caused toxicity: low blood pressure, vomiting, irregular heartbeat and, rarely, death [9]. That's far above tablet amounts, but it's why kidney function matters.
How did trials have people take hydrogen tablets?
One tablet in 250–500 mL of water, drunk as soon as it finished dissolving, two or three times a day.
- Water: 250 mL [3, 6], 330 mL [4] or 500 mL [2] per tablet. One trial used cool water (12–18 °C) [3].
- Timing: "immediately" once dissolved [4], "in one gulp" [3], or within about 3 minutes [2].
- Frequency: twice [2, 6] or three times a day [3, 4]. One small study used five tablets a day [8].
Speed matters because the hydrogen escapes. In an open 500 mL beaker, a freshly dissolved tablet measured about 10 mg/L but fell to about 1.6 mg/L, the normal saturation level, within 30 minutes [1]. The trials we read didn't say whether they used a closed container. In a lab test of stored hydrogen water, aluminum and stainless-steel containers lost almost no hydrogen over 12 hours, while plastic and glass lost about half within 4 hours [11]. More on concentration: hydrogen water ppm levels; trial doses: how much hydrogen water per day.
Tablets vs. electrolysis bottles vs. ready-to-drink pouches
The main differences are when the hydrogen is made, whether magnesium comes with it, and how you pay.
| Magnesium tablets | Ready-to-drink pouches, cans or bottles | Electrolysis bottles and generators | |
|---|---|---|---|
| How hydrogen gets in | Made in your glass by the magnesium reaction [1] | Made before packaging, then sealed; metal containers hold it well [11] | Electric current splits water [13] |
| Concentration measured | ≈10 mg/L right after dissolving, near 1.6 mg/L within 30 min [1]; >4 mg/L in one trial [4] | ≥4.66 mg/L in one trial's bottles [14]; lab-made pressure bottles held about 7–10 ppm for up to a week sealed, but fell within 1–2 hours of opening [12] | 0.78–0.90 mg/L from one generator [11]; new water ionizers typically 0.2–1.2 mg/L [13] |
| Adds magnesium | Yes | No | No |
| Cost structure | Per tablet, ongoing | Per serving, ongoing | Device up front, then upkeep |
| Convenience | Small and portable; wait, then drink | No preparation | Reusable; output depends on the device, the water and electrode cleaning [13] |
These figures come from different studies and methods, so they aren't a head-to-head test. What counts is the concentration when you drink, not the number on a label.
How do you make hydrogen water?
Use a product built for it, or buy it ready-made. The four common routes:
- Magnesium tablets or sticks. Drop a tablet into water in a bottle you can close, and drink it once it has dissolved. Its magnesium stays in the drink (see above) [1].
- Electrolysis bottles and countertop generators. An electric current splits water and releases hydrogen. One portable generator made about 0.8–1.0 mg/L from tap or mineral water in lab tests [11]. Water ionizers also make the water alkaline; see hydrogen water vs alkaline water.
- Pressurized bottles. Hydrogen made in a sealed chamber pressurizes the bottle and forces more gas into the water. Two lab designs reached about 7–10 ppm and held it for a week while sealed [12].
- Ready-made pouches or cans. Hydrogen is dissolved and sealed in at the factory; metal packaging holds it best [11].
What decides how much you actually drink:
- Keep it closed, then drink it fast. Pressurized bottles lost a significant share within an hour of opening; the researchers advised drinking within 2 hours, with as little air space in the bottle as possible [12]. A tablet in an open beaker fell to ordinary saturation within 30 minutes [1].
- Store it in metal. Plastic and glass containers lost about half their hydrogen in 4 hours; aluminum and stainless steel held nearly all of it for 12 hours [11].
- Skip hot water. One generator made about the same amount from 1.5 to 30 °C, but less at 40–50 °C [11].
- Use the water your device expects. Electrolysis needs some minerals: purified water made very little hydrogen in one generator, and hard water slightly less than soft [11]. Ionizers need roughly 50 mg/L of minerals in the tap water [13].
- Keep electrodes clean. Mineral scale cut some ionizers' output from nearly 1 mg/L to under 0.01 mg/L within two weeks; cleaning with citric acid restored it [13].
What not to do:
- Don't mix your own chemicals. In the lab pressure bottles, the gas-making mix was sealed off so it never touched the drinking water [12]. Metal powders, acids or drain cleaner mixed at home have no such barrier. Baking soda won't work either: with an acid, it releases carbon dioxide, not hydrogen.
- Don't electrolyze salt water or rig your own electrodes. Electrolyzing water that contains chloride forms chlorine compounds at the positive electrode, and even commercial platinum-coated electrodes can shed metal under harsh settings [13]. Homemade electrodes are an unknown.
- Don't collect or store hydrogen gas. Hydrogen mixed with air can ignite at 4% to 75%, and it burns with an almost invisible flame [15]. Fully dissolved hydrogen can't be ignited [13], but gas building up in a closed space can. See our guide to hydrogen machines for home use.
How to check what you made. Test at the time you'd drink it, using hydrogen-specific reagent drops (a titration method also used in lab studies [12]) or a dissolved-hydrogen meter, not an ORP meter, which mostly reflects pH [13]. See hydrogen water ppm levels.
What the evidence doesn't show
- Long-term safety. The longest tablet trial we found lasted 24 weeks [3]. Most lasted 3–8 weeks.
- Benefit. Results are mixed: one 24-week trial reported metabolic improvements [3], while the largest trial found no benefit [6]. Our honest overall verdict is in is hydrogen water real or fake?
- What people actually drank. One trial said it couldn't track whether people followed the protocol [4], and hydrogen levels fall within minutes.
- Side effects of magnesium itself. In the four tablet trials that described their placebo tablets, those also contained magnesium, so tablet side effects weren't compared with a magnesium-free drink [1, 2, 4, 6].
- Independence. The same tablet manufacturer donated, sponsored or supplied the product in five of the six studies above, and a company employee co-authored three [2, 3, 4, 7, 8]. That doesn't make the results wrong, but independent replication is needed. See our methodology and more hydrogen water studies.
Frequently asked questions
Do hydrogen tablets have side effects?
Some people report digestive effects such as diarrhea or stomach pain. In the largest trial, these were about as common with placebo tablets that also contained magnesium. Smaller trials reported few or no side effects, but they were short and small. The magnesium in the tablets is the main thing to watch.
How many hydrogen tablets can I take a day?
Trials used 2 to 5 tablets a day and didn't test more. The practical limit is magnesium: the adult upper limit is 350 mg a day from supplements, including tablets. At 80 mg per tablet, four tablets supply 320 mg, so check your label and count other magnesium supplements.
Can hydrogen tablets cause diarrhea?
They can. Too much supplemental magnesium can cause diarrhea, nausea and cramping, and diarrhea is why the 350 mg limit exists. In the 675-person COVID-19 trial, diarrhea or abdominal pain was reported by 44 people on hydrogen tablets and 48 on placebo tablets that also contained magnesium.
Are hydrogen tablets safe if I have kidney disease?
Ask your nephrologist first. Kidneys that don't work well can't clear extra magnesium, which raises the risk of magnesium toxicity. No tablet trial we found tested safety in people with kidney disease.
What are the benefits of hydrogen tablets?
The evidence is limited and mixed. A 24-week trial in 60 adults with metabolic syndrome reported better cholesterol and blood sugar markers than placebo, but a 675-person trial found no benefit for COVID-19, and most other tablet studies were small. None establish that tablets treat or prevent any disease.
How do you make hydrogen water at home?
Use a product made for it: drop a magnesium hydrogen tablet into water in a closed bottle, or use an electrolysis bottle or generator with the water its maker recommends. Drink it within minutes of making or opening it, and store it only in a sealed metal container. Don't mix your own chemicals, electrolyze salt water or collect hydrogen gas. To see how much you made, use hydrogen-specific test drops, not an ORP meter.
Sources
- LeBaron TW, et al. Acute supplementation with molecular hydrogen benefits submaximal exercise indices. Randomized, double-blinded, placebo-controlled crossover pilot study. Journal of Lifestyle Medicine. 2019. PubMed · Our summary
- Ogannisyan M, et al. Hydrogen-rich water decreases muscle damage and improves power endurance in elite athletes: a randomized, double-blinded, placebo-controlled trial. Journal of Lifestyle Medicine. 2025. PubMed · Our summary
- LeBaron TW, et al. The effects of 24-week, high-concentration hydrogen-rich water on body composition, blood lipid profiles and inflammation biomarkers in men and women with metabolic syndrome: a randomized controlled trial. Diabetes, Metabolic Syndrome and Obesity. 2020. PubMed · Our summary
- Kura B, et al. Biological effects of hydrogen water on subjects with NAFLD: a randomized, placebo-controlled trial. Antioxidants. 2022. PubMed
- Sumbalová Z, et al. The effect of adjuvant therapy with molecular hydrogen on endogenous coenzyme Q10 levels and platelet mitochondrial bioenergetics in patients with non-alcoholic fatty liver disease. International Journal of Molecular Sciences. 2023. PubMed · Our summary
- Gaboreau Y, et al. Molecular hydrogen for outpatients with COVID-19 (Hydro-COVID): a phase 3 randomised, triple-blinded, pragmatic, placebo-controlled, multicentre trial. Journal of Clinical Medicine. 2024. PubMed · Our summary
- Todorovic N, et al. The effects of 8-week hydrogen-rich water consumption on appetite, body composition, sleep quality, and circulating glucagon-like peptide-1 in obese men and women (HYDRAPPET): a randomized controlled trial. Medicina. 2025. PubMed · Our summary
- Singh RB, et al. Can hydrogen water enhance oxygen saturation in patients with chronic lung disease? A non-randomized, observational pilot study. Diseases. 2023. PubMed · Our summary
- NIH Office of Dietary Supplements. Magnesium — Fact Sheet for Health Professionals (updated January 6, 2026). ods.od.nih.gov
- Costello R, et al. Perspective: call for re-evaluation of the tolerable upper intake level for magnesium supplementation in adults. Advances in Nutrition. 2023. PubMed
- Tanaka Y, et al. Dependencies of hydrogen-water on mineral-based hardness, temperatures and the container materials, and effects of the oral washing and drinking. Medical Gas Research. 2020. PubMed · Our summary
- Kurokawa R, et al. Convenient methods for ingestion of molecular hydrogen: drinking, injection, and inhalation. Medical Gas Research. 2015. PubMed · Our summary
- LeBaron TW, et al. Electrolyzed-reduced water: Review II: safety concerns and effectiveness as a source of hydrogen water. International Journal of Molecular Sciences. 2022. PubMed · Our summary
- Wu F, et al. Effects of hydrogen-rich water on blood uric acid in patients with hyperuricemia: a randomized placebo-controlled trial. Heliyon. 2024. PubMed · Our summary
- NOAA Office of Response and Restoration. Hydrogen — chemical datasheet (lower and upper explosive limits 4% and 75%). CAMEO Chemicals. cameochemicals.noaa.gov
Conflicts of interest in sources cited in the how-to section: the authors of source 12 work for MiZ Co., a Japanese company that develops hydrogen-generating devices. The authors of source 13 are affiliated with the Molecular Hydrogen Institute, a nonprofit that promotes hydrogen research, and H2 Analytics, a hydrogen-testing company that has certified products for Echo Technologies, which funds this site.
How we wrote this: drafted with AI assistance from the sources above and checked against each source by the Hydrogen Studies editorial team. This is general information, not medical advice — talk to your clinician before changing any treatment.