Magnesium Cream Study Shows 8.5% Rise-but Is It Enough?
Magnesium cream study: why the 8.5% rise is not simple
The headline answer is that the reported 8.54% increase in serum magnesium came from a small 2017 pilot trial, and it does not prove that transdermal magnesium cream reliably raises magnesium levels in most people. The study found a signal, but the main result was not statistically significant overall, the sample was tiny, and the strongest effect appeared only in a subgroup of non-athletes.
What the study actually found
The paper, published in 2017, randomized 25 adults to receive either a magnesium cream delivering 56 mg/day or a placebo cream for two weeks, then measured serum and urinary magnesium before and after the intervention. In the magnesium group, serum magnesium rose from 0.82 to 0.89 mmol/L, which the authors described as an 8.54% increase, while urinary magnesium rose 9.1%; by comparison, the placebo group showed smaller shifts, including a 2.6% serum increase and a 32% drop in urinary magnesium.
That sounds impressive at first glance, but the key point is that the overall serum change in the magnesium group was not statistically significant on its own, with p=0.29, and the urinary change was also not significant, with p=0.48. The only statistically significant result reported was in a subgroup of non-athletes, which means the headline percentage should not be treated as a universal effect.
Why the percentage can mislead
An 8.54% rise sounds large, but percentage changes can overstate practical importance when the starting value is already close to normal range and the sample is very small. In this trial, the absolute change in serum magnesium was 0.07 mmol/L, which is a modest shift and may reflect normal biological variation, hydration differences, diet, or short-term fluctuations rather than a robust transdermal effect.
Another reason the figure is tricky is that pilot studies are designed to test feasibility and generate hypotheses, not to settle clinical questions. With only 25 participants over two weeks, the study is underpowered for strong claims, especially when the result depends on subgroup analysis.
Study design limits
The trial was single-blind, parallel-group, and short duration, which leaves several weaknesses that matter for interpretation. A small sample makes results unstable, a two-week window may be too short to assess meaningful body magnesium repletion, and the authors themselves noted that future studies should test higher doses for longer periods.
The dosage also matters. The intervention used 56 mg/day of magnesium in cream form, which the paper described as low compared with many commercial transdermal products, so even a real effect at this dose would not automatically translate to stronger over-the-counter creams.
| Measure | Magnesium cream group | Placebo group |
|---|---|---|
| Participants | Small pilot subset within n=25 total | Small pilot subset within n=25 total |
| Intervention | 56 mg/day for 14 days | Placebo cream for 14 days |
| Serum magnesium change | 0.82 to 0.89 mmol/L, +8.54% | 0.77 to 0.79 mmol/L, +2.6% |
| Urinary magnesium change | +9.1% | -32% |
| Statistical significance | Not significant overall; subgroup signal in non-athletes | No significant change |
What this means for consumers
The study supports the possibility that magnesium applied to skin may be absorbed to some extent, but it does not establish that magnesium cream is a dependable treatment for deficiency or cramps. For people trying to correct low magnesium, oral supplementation and diet still have a much larger evidence base than transdermal products, and the cream evidence remains preliminary.
It is also important to separate "magnesium got into the body" from "magnesium reliably improved health outcomes." The study only measured biomarkers, not symptoms, long-term deficiency correction, muscle function, sleep quality, blood pressure outcomes, or clinical endpoints.
How to read the evidence
- Start with the study type: this was a pilot trial, not a definitive clinical trial.
- Check the sample size: 25 participants is too small for broad claims.
- Look at statistical significance: the 8.54% serum rise was not significant overall.
- Ask whether the result applies broadly: the clearest signal was in a subgroup of non-athletes.
- Compare biomarkers with outcomes: blood and urine changes do not automatically mean clinical benefit.
Historical context
Interest in transdermal magnesium grew because many consumers wanted a non-pill option, especially for people who dislike oral supplements or blame tablets for stomach upset. The 2017 study by Kass and colleagues, linked to the University of Hertfordshire and indexed in PLOS ONE, became one of the most cited human experiments in this space because it was among the first to test magnesium cream against placebo in people rather than only in lab or skin-permeation models.
That historical importance should not be confused with proof. Later commentary and related coverage highlighted the study as suggestive, but not conclusive, and the broader literature still treats transdermal magnesium as an area where better trials are needed.
What a stronger study would need
A convincing follow-up would need many more participants, longer treatment duration, clearly defined magnesium-deficient and magnesium-replete groups, and outcomes that go beyond blood tests. It would also need standardized cream formulation, better dosing comparisons, and careful control of diet, exercise, and hydration, because these factors can affect serum and urinary magnesium measurements.
Until then, the safest interpretation is that the 8.54% figure is an interesting pilot signal, not a settled finding.
"Larger percentage rise" is not the same as "clinically proven treatment," especially when the result comes from a two-week pilot study with subgroup significance only.
Practical takeaway
If someone is considering magnesium cream, the most evidence-based expectation is that it may help some users, but it should not be assumed to correct deficiency or replace oral magnesium without medical guidance. The 8.5% rise is real as a reported study result, but its meaning is limited by the study's size, duration, and statistical uncertainty.
Expert answers to Magnesium Cream Study Shows 85 Rise But Is It Enough queries
Does the study prove magnesium cream is absorbed through skin?
No. It suggests possible transdermal absorption, but the evidence is preliminary and based on a small pilot trial with limited statistical strength.
Was the 8.54% increase statistically significant?
No, not for the overall serum result in the main group. The study reported statistical significance only in a subgroup of non-athletes.
Can magnesium cream treat deficiency?
The study does not prove that. It measured biomarkers over two weeks, not clinical correction of deficiency or symptom relief.
Why do headlines focus on the 8.5% figure?
Because percentage changes are easy to understand and sound larger than the underlying absolute change. In a small pilot study, that can make a modest signal look more definitive than it really is.