ReMag is a liquid magnesium supplement that is generally safe for healthy adults when used within standard magnesium dosing limits, but it comes with some important caveats. The product has not been independently verified for safety by the FDA, and the company behind it received a formal FDA warning letter in 2017 for making unapproved drug claims. Understanding what’s in it, what the manufacturer claims versus what’s proven, and where the real risks lie will help you make a more informed choice.
What ReMag Actually Contains
ReMag is a concentrated liquid magnesium solution at 60,000 parts per million, using what the manufacturer calls “picometer-sized” magnesium ions that are 99.99% pure. The company, RnA ReSet, markets it as a form of magnesium small enough to be absorbed directly into cells, bypassing the digestive tract and avoiding the laxative effect that many magnesium supplements cause.
These are marketing claims, not conclusions from peer-reviewed research. No independent clinical trials have tested ReMag specifically to confirm that its particle size improves absorption or that it enters cells differently than other liquid magnesium products. The term “picometer magnesium” is unique to this brand and is not a recognized category in nutritional science. That doesn’t automatically mean the product is harmful, but it does mean the absorption and bioavailability claims rest on the company’s word rather than published evidence.
The FDA Warning Letter
In June 2017, the FDA issued a warning letter to New Capstone, Inc., the company operating the RnA ReSet website. The agency found that the website’s health claims, including testimonials suggesting ReMag could treat or prevent diseases, made the product an unapproved drug under federal law. The FDA stated that ReMag was “not generally recognized as safe and effective” for the uses described on the site and warned that continued violations could lead to product seizure or legal action.
This letter did not mean the FDA found the magnesium itself to be dangerous. It meant the company was making therapeutic claims that only an approved drug can legally make. However, it’s a meaningful red flag for consumers because it signals that the manufacturer was willing to overstate what the product can do. When a company makes unverified treatment claims, it raises fair questions about the rigor behind its other claims, including those about safety and absorption.
No Evidence of Third-Party Testing
One practical concern is that ReMag does not appear to carry any third-party certification from organizations like NSF International or USP, which independently test supplements for purity, potency, and heavy metal contamination. These certifications are voluntary, and many supplement brands skip them, but they’re one of the few ways consumers can verify that what’s on the label matches what’s in the bottle. Without that verification, you’re relying entirely on the manufacturer’s quality control.
General Magnesium Safety Limits
Regardless of brand, all supplemental magnesium carries the same safety boundaries. The NIH sets the tolerable upper intake level for supplemental magnesium at 350 mg per day for adults. This limit applies to magnesium from supplements and medications only, not from food. For children, the upper limit ranges from 65 mg (ages 1 to 3) up to 350 mg (ages 9 and older). Pregnant and lactating women share the same 350 mg ceiling.
Taking more than 350 mg per day from supplements doesn’t guarantee harm, but it increases the risk of side effects. Common ones include nausea, stomach cramps, vomiting, and diarrhea. ReMag’s manufacturer claims its formulation avoids the laxative effect, though this hasn’t been confirmed in independent studies. Even if the product does cause less digestive upset, that doesn’t change the total amount of magnesium entering your bloodstream, which is where the more serious risks come in.
When Magnesium Becomes Dangerous
The real safety concern with any magnesium supplement, ReMag included, is a condition called hypermagnesemia, where magnesium levels in the blood climb too high. In healthy people with normal kidney function, this is rare because the kidneys efficiently flush excess magnesium. The risk rises sharply for people with reduced kidney function, including those with chronic kidney disease and many older adults whose kidney filtration has naturally declined.
Early signs of magnesium buildup include low blood pressure that doesn’t respond to treatment, dizziness, nausea, and general weakness. More severe cases can cause confusion, difficulty breathing, drowsiness, and dangerous heart rhythm changes. At very high levels, magnesium toxicity can lead to muscle paralysis, coma, and cardiac arrest. Symptomatic hypermagnesemia typically only occurs at blood levels above roughly 1.6 mmol/L, and most cases involve people with kidney problems who are also taking magnesium-containing laxatives or antacids.
If you have any degree of kidney disease, magnesium supplementation requires close monitoring. Research published in the journal Nutrients found that magnesium can be given safely in chronic kidney disease under medical supervision, but experts recommend against it if blood magnesium levels already exceed 1.2 mmol/L. This applies to all magnesium supplements, not just ReMag.
Who Should Be Cautious
Beyond kidney disease, certain groups face higher risk from supplemental magnesium. People taking medications that affect kidney function, heart rhythm drugs, or certain antibiotics can experience interactions. Anyone on a prescription diuretic may already have altered magnesium levels in either direction, making self-supplementation unpredictable.
The liquid format of ReMag can actually make dosing errors more likely than with pills or capsules. A concentrated solution at 60,000 ppm means small volume differences translate to meaningful changes in the amount of magnesium you consume. Careful measuring matters, especially if you’re giving it to children or starting at a high dose.
The Bottom Line on Safety
The magnesium in ReMag is not inherently unsafe for most healthy adults. Magnesium is an essential mineral, and supplementing within the 350 mg daily limit is well tolerated by people with normal kidney function. What makes ReMag harder to evaluate than many competitors is the combination of unverified marketing claims, an FDA warning letter for overstating what the product can do, and no publicly available third-party testing for purity. The product may work perfectly well as a basic magnesium supplement, but you’re paying a premium for claims that haven’t been independently substantiated. If reliable quality assurance matters to you, look for a magnesium supplement that carries a USP or NSF seal.