The Magnesium Investigation | NF Supplements
Logan King

[ A note from Logan King ]

Hi, I’m Logan.

I get supplements tested by independent labs and share the results.

I buy supplements off the shelf and send them to labs to check what’s inside. I share the results on my YouTube channel, Logan Talks Health.

Logan Talks Health YouTube channel profile, with Logan’s photograph and his description of buying supplements off the shelf for third-party testing
Channel profileVisit my channel ↗

Four of my earlier investigations

Earlier videos
01 / Omega-3

I 3rd-Party Tested The Top UK Omega-3 Supplements
02 / Vitamin D

I 3rd-Party Tested 7 Of The UK’s Top Vitamin D Brands
03 / Protein

I 3rd-Party Tested The UK’s Top Protein Products
04 / Nutrition Geeks

I 3rd Party Tested The Fastest Growing Supplement Company In The UK

[ Start here ]

A quick guide to the evidence.

Three ways to explore what we found.

01 / Understand the basicsWhy the type matters.Learn what glycinate, citrate and oxide mean. ↓02 / Check your brandSee the lab reports.Choose a brand. See what the lab found. ↓03 / Hear the expertsWatch the interviews.Hear scientists explain the results. ↓

Each result is for the product we tested. I own NF Supplements, which is included in the comparison.

[ The new documentary ]

The magnesium
investigation.

Logan standing behind the UK and US magnesium supplements featured in his investigation
Fig. 01 The magnesium supplements I investigated.

I sent these UK and US supplements to a lab. The results below apply to the batches listed for each brand. A batch is a group of products made in the same production run.

UK
Nutrition Geeks, Free Soul, Zipvit, HEIGHTS, SportSupplies and British Supplements.
US
Thorne, Pure Encapsulations and BioEmblem.
My brand
NF Supplements, included for comparison.

The Nutrition Geeks pack listed three types of magnesium. The lab found those three and two more.

Dr Nikolay Tumanov checked the powders using X-rays. These reveal patterns that can be matched to known ingredients, like fingerprints. This helped him identify what was inside.

What do the different types mean? ↓

FULL INVESTIGATION PREMIERES IN…

00Days
00Hours
00Minutes
00Seconds

Premiere: 13 November 2026 at 4:00 pm GMT
Video coming soon
Documentary thumbnail: Logan holding a large capsule illustration labelled 50% glycinate and 50% oxide, with supplement products in the background
30-minute investigation
The evidence file
03Lab reports10Products tested02Expert interviews

[ Reading a magnesium label ]

Why are there different types of magnesium?

Magnesium is a mineral. In a supplement, it is joined to another ingredient. That gives it a name such as magnesium glycinate, magnesium citrate or magnesium oxide.

The other ingredient adds weight. So 100 mg of powder is not 100 mg of magnesium. The amount of magnesium itself is called elemental magnesium. “mg” means milligrams, a measure of weight.

The same amount of powderHow much is magnesium?
Magnesium itselfThe other part
GlycinateAbout 14 mg out of 100 mg
CitrateAbout 16 mg out of 100 mg
HydroxideAbout 42 mg out of 100 mg
OxideAbout 60 mg out of 100 mg

Each bar represents 100 mg of pure powder. These examples use forms with no water built into their structure. Forms that include water contain less magnesium per 100 mg. Expert explanation ↗ · Hydroxide reference ↗

[ Why the ingredients matter ]

Why mix in oxide or hydroxide?

More magnesium. Fewer capsules.

Oxide and hydroxide pack more magnesium into the same weight of powder. Mixing them with glycinate can help a brand fit the amount on the label into fewer capsules. This mixing is called buffering.

It can cost less to make

Dr Tumanov explained that oxide is cheaper than glycinate, although the saving per bottle can be small. Fewer capsules can also mean lower filling and packaging costs.

An example, not a suggested doseThe same 350 mg of magnesium can take more capsules.
Ingredients How much is magnesium? Powder needed Capsules
Pure glycinate 11.7–14.1% ~2,480–3,000 mg 3–4 capsules
75% glycinate
25% hydroxide		 21% ~1,670 mg 2 capsules
75% glycinate
25% oxide		 26% ~1,360 mg 2 capsules

This example allows up to 950 mg of powder per capsule. Glycinate alone needs 3–4 capsules; the mixtures need 2. Some glycinate includes water in its structure, which adds weight and explains the 3–4 range. The mixtures use the form without that water. The percentages in the first column describe the powder mixture.

Does your body take in all of it?

No. The amount you swallow is not the amount your body absorbs. In a study of 46 people taking equal amounts, oxide was absorbed less well than citrate and an amino-acid form after 60 days.

More about the studies

An amino acid is a building block of protein. Researchers estimated absorption using magnesium measured in urine. A separate study in ten men estimated about 15% absorption for the hydroxide product it tested. These results do not give an absorption percentage for the brands on this page.

Read the oxide study ↗ · Read the hydroxide study ↗

Finding it does not tell us why it’s there

The lab can identify ingredients. It cannot prove why a company used them. Free Soul’s label described its mixture as buffered. For Thorne, the scientist thought some ingredients had not fully reacted during manufacturing.

See the results ↓

[ 01 / Results by brand ]

How much comes from oxide or hydroxide?

Orange shows the estimated amount of magnesium supplied by oxide or hydroxide. Green shows the rest. Choose a brand to read what the lab found.

How to read the percentages: 60% means about 60 out of every 100 mg of magnesium came from oxide or hydroxide. It does not mean 60% of all the powder was oxide.

10 brands
Brand / batchSources of magnesiumFrom oxide / hydroxideWhat the label says
Free SoulUK · Batch 52502Label says “buffered”

What the number means. At least 66% is an estimate that depends on the label’s amounts being correct.

What the label says. The label describes the mixture as buffered, but the report says it does not name magnesium oxide.

What the lab found. Oxide and a small amount of glycinate. Another ingredient, brushite, made the heating test harder to interpret.

Read the full lab report ↗
See this brand’s lab chart ↓
ThorneUS · Batch 6220902Oxide not listed

What the number means. The signed report estimates that about 65% of the magnesium comes from oxide.

What the label says. Glycinate, with 120 mg of magnesium.

What the lab found. Glycinate, oxide and glycine that was not joined to magnesium. The scientist thought the ingredients had not fully reacted during manufacturing. The report found 148 mg of magnesium.

Read the full lab report ↗
See this brand’s lab chart ↓
ZipvitUK · Batch QA26010075Hydroxide not listed

What the number means. About 58% of the magnesium is estimated to come from hydroxide.

What the label says. Glycinate, with 200 mg of magnesium per tablet.

What the lab found. Glycinate and hydroxide, plus what was probably cellulose, a filler. The report found 210 mg of magnesium per tablet.

Read the full lab report ↗
See this brand’s lab chart ↓
Nutrition GeeksUK · Batch 0428080Neither listed

What the number means. The updated report concludes that approximately 50–60% of the magnesium comes from oxide and hydroxide combined.

What the label says. Glycinate, malate and citrate, supplying 384 mg of magnesium from 1,800 mg of ingredients.

What the lab found. The three named types, plus oxide and hydroxide. The report says those two extra types were not listed on this batch’s label.

Read the full lab report ↗
See this brand’s lab chart ↓
HEIGHTSUK · Batch 54827Oxide not listed

What the number means. About 55% of the magnesium is estimated to come from oxide.

What the label says. Glycinate, with 150 mg of magnesium per capsule.

What the lab found. Glycinate and oxide. The report found 158 mg of magnesium per capsule.

Read the full lab report ↗
See this brand’s lab chart ↓
BioEmblemUS · Batch 2511007Oxide not listed

What the number means. The signed report estimates that about 54% of the magnesium comes from oxide.

What the label says. The tested product is listed as magnesium glycinate in the report.

What the lab found. Glycinate, oxide and some material the test could not identify.

Read the full lab report ↗
See this brand’s lab chart ↓
SportSuppliesUK · Batch 1502Oxide not listed

What the number means. About 52% of the magnesium is estimated to come from oxide.

What the label says. Glycinate, with 315 mg of magnesium per serving. A serving is the amount the label tells you to take.

What the lab found. Glycinate and oxide. The report found 302 mg of magnesium per serving.

Read the full lab report ↗
See this brand’s lab chart ↓
Pure EncapsulationsUS · Batch 50388578Trace onlyProbable small impurity

What the number means. Less than 1% of the powder’s weight was oxide. This is a different measurement from the magnesium-source percentages shown for other brands, so no comparison bar is shown.

What the label says. Glycinate, with 120 mg of magnesium.

What the lab found. Mainly glycinate, with a probable very small amount of oxide. The report puts oxide below 1% of the powder’s weight and calls that an acceptable trace. It found 127 mg of magnesium.

Read the full lab report ↗
See this brand’s lab chart ↓
British SupplementsUK · Batch 20231101Neither found

What the result means. The lab did not find oxide or hydroxide in this sample. That does not prove absolute absence.

What the label says. Glycinate, malate and aspartate: three types of magnesium.

What the lab found. Glycinate and malate were identified directly. The way the powder behaved when heated also supported the presence of aspartate.

Read the full lab report ↗
See this brand’s lab chart ↓
NF SupplementsMy brand · Batch N1796Neither found

What the lab found. Water-free magnesium glycinate (also called anhydrous bisglycinate). No other crystalline ingredients were detected, including oxide or hydroxide.

What else is in the powder? The heating test estimates 89% magnesium glycinate and 11% cellulose, a filler, by powder weight, ignoring minor excipients.

Magnesium amount. The reported dose is 338 mg; the lab found 370 mg by thermal analysis.

Read the full lab report ↗
See this brand’s lab chart ↓

Seven of the nine other brands had more than a tiny trace of oxide or hydroxide. The tested NF product had neither found. These results cover the batches tested. The percentages are estimates of where the magnesium came from, not the weight of the whole powder. Pure’s less-than-1% result is by powder weight and is shown separately from the bars.

[ 02 / Lab reports by brand ]

See the lab reports.

Tap a brand to see what the lab found and open its report.

Updated signed reports are now available below for all ten brands shown.

Nutrition Geeks

UK · Batch 0428080

50–60% from oxide + hydroxide

Original lab chart for Nutrition Geeks, batch 0428080: black line for the tested powder and coloured lines for known ingredients
Chart from the updated report · 30 September 2026 · page 2Enlarge the chart ↗

What the lab found

50–60%of the magnesium comes from oxide and hydroxide combined.
  • Oxide found
  • Hydroxide found

Glycinate, citrate and malate were present, as the label said. The lab also found oxide and hydroxide, which were not listed. The updated report confirms the 50–60% combined share shown above.

Read the full report · 4 pages ↗

Free Soul

UK · Batch 52502

66%+ from oxide

Original lab chart for Free Soul, batch 52502: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 14Enlarge the chart ↗

What the lab found

66%+of the magnesium comes from oxide (minimum estimate).
  • Oxide found
  • Hydroxide not detected

The lab found oxide, a small amount of glycinate, and another ingredient called brushite. The label described the mixture as buffered.

Read the full report · page 15 ↗

Zipvit

UK · Batch QA26010075

~58% from hydroxide

Original lab chart for Zipvit, batch QA26010075: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 6Enlarge the chart ↗

What the lab found

~58%of the magnesium comes from hydroxide.
  • Oxide not detected
  • Hydroxide found

The lab found glycinate and hydroxide, plus what was probably cellulose, a filler.

Read the full report · page 7 ↗

HEIGHTS

UK · Batch 54827

~55% from oxide

Original lab chart for HEIGHTS, batch 54827: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 8Enlarge the chart ↗

What the lab found

~55%of the magnesium comes from oxide.
  • Oxide found
  • Hydroxide not detected

The lab found glycinate and oxide in the powder.

Read the full report · page 9 ↗

SportSupplies

UK · Batch 1502

~52% from oxide

Original lab chart for SportSupplies, batch 1502: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 10Enlarge the chart ↗

What the lab found

~52%of the magnesium comes from oxide.
  • Oxide found
  • Hydroxide not detected

The lab found glycinate and oxide in the powder.

Read the full report · page 11 ↗

British Supplements

UK · Batch 20231101

Oxide and hydroxide not found

Original lab chart for British Supplements, batch 20231101: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 17Enlarge the chart ↗

What the lab found

  • Oxide not detected
  • Hydroxide not detected

The lab found glycinate and malate. It did not find oxide or hydroxide in this sample.

Read the full report · page 17 ↗

Thorne

US · Batch 6220902

~65% from oxide

Original lab chart for Thorne, batch 6220902: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 2Enlarge the chart ↗

What the lab found

~65%of the magnesium comes from oxide.
  • Oxide found
  • Hydroxide not detected

The lab found glycinate, oxide and glycine that had not joined to magnesium.

Read the full report · page 3 ↗

Pure Encapsulations

US · Batch 50388578

Less than 1% oxide · by powder weight

Original lab chart for Pure Encapsulations, batch 50388578: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 4Enlarge the chart ↗

What the lab found

<1%of the powder’s weight is oxide — a small trace.
  • Less than 1% oxide by powder weight
  • Hydroxide not detected

The main ingredient was glycinate. The lab reported less than 1% oxide by powder weight, described as an acceptable trace.

Read the full report · page 5 ↗

BioEmblem

US · Batch 2511007

~54% from oxide

Original lab chart for BioEmblem, batch 2511007: black line for the tested powder and coloured lines for known ingredients
Chart from the report signed 9 November 2026 · page 12Enlarge the chart ↗

What the lab found

~54%of the magnesium comes from oxide.
  • Oxide found
  • Hydroxide not detected

The lab found glycinate, oxide and some material it could not identify.

Read the full report · page 13 ↗

NF Supplements

My brand · Batch N1796

Oxide and hydroxide not found

Original lab chart for NF Supplements, batch N1796: tested powder compared with water-free magnesium glycinate
Chart from the report signed 9 November 2026 · page 2Enlarge the chart ↗

What the lab found

  • Oxide not detected
  • Hydroxide not detected

The lab found water-free magnesium glycinate. Its heating test estimates 89% glycinate and 11% cellulose by powder weight, ignoring minor excipients. Cellulose is a filler.

The reported magnesium dose is 338 mg; the lab found 370 mg.

This report names the product “HD Supplements”. Batch N1796 · signed 9 November 2026.

Read the full report · 3 pages ↗
What do the lines on the lab charts mean?
1. The black line is the tested powder

The lab shines X-rays at the powder and records a pattern. The spikes are signals picked up by the test.

2. Coloured lines are known ingredients

The scientist looks for spikes in matching positions. This helps identify which ingredients are present.

3. The written result explains the finding

You don’t need to read the chart yourself. The summary below each one explains what was found. The chart does not measure how much your body absorbs.

These charts are reproduced unchanged from the linked lab reports. Results apply to the batches tested. “Not detected” does not guarantee that an ingredient is completely absent from every product.

Download the full lab reports.

30 Sep 2026

Nutrition Geeks

Batch 0428080 · updated signed report · 4 pages

Signed 9 Nov 2026

NF Supplements

Batch N1796 · signed report · 3 pages

Signed 9 Nov 2026

Multi-brand laboratory report

Updated signed report · 9 samples · 18 pages
More lab filesOriginal test data ZIP download ↓Earlier October report Word archive ↓Earlier September report Archive · NF batch N1769 ↗Earlier October PDF Archive ↗
How did the lab check the ingredients?
01 / Identify the ingredients

The lab used X-rays to record patterns made by tiny crystals in the powder. It compared these with patterns from known ingredients. This method is called X-ray diffraction, or XRD.

02 / Check the amounts

The lab also heated the powder and measured how much weight it lost. Together with the X-ray results, this can help estimate how much of each ingredient is present. This heating test is called thermal analysis.

03 / Know the limits

Some ingredients do not produce a clear X-ray pattern. Fillers can also make the heating test harder to interpret. The reports explain where the results are uncertain. Neither test measures absorption in people.

[ 03 / Interviews ]

Hear from the scientists.

Meet the scientist who tested the powders and a researcher who studies magnesium.

01 / The lab tests · Dr Nikolay Tumanov

Watch full interview ↗

Dr Nikolay Tumanov

Scientist who tested the powders · University of Namur

Why the ingredients on the label should match what’s inside.

Watch on YouTube ↗
On ingredients missing from the label
“The cases where even buffering is not on the label, that should not exist at all.”
On trusting a brand
“If somebody is trying to fool you in this part, why you should trust it for the rest.”

02 / The chemistry · Prof. Jürgen Vormann

Watch full interview ↗

Prof. Jürgen Vormann

Magnesium researcher · Institute for Prevention and Nutrition

What magnesium labels mean, and why the type matters.

Read the interview ↗Watch on YouTube ↗
On the limits of chemistry
“You can’t fool the chemistry, this is not possible.”
When a label says magnesium citrate
“The magnesium should only come from the citrate and not from the oxide.”

Quotes from the interview transcripts, with filler words omitted. Watch the full conversations for context.

NF Supplements · My brand

Choose magnesium glycinate.

Buy Pure Magnesium Glycinate
[ Logan Talks Health / Archive ]

Watch on YouTube ↗