Magnesium is one of the most widely supplemented minerals in the UK — and one of the most commonly misunderstood. With over a dozen different forms available, wildly different price points, and a tangle of marketing claims, choosing the right magnesium supplement can feel overwhelming. This guide breaks it all down factually.
📋 In This Guide
What Is Magnesium and Why Does It Matter? What Can Magnesium Legally Claim in the UK? Magnesium Deficiency: How Common Is It? Types of Magnesium: A Complete Comparison Magnesium Glycinate: Why It Dominates the Market Why Some Supplements Use Multiple Forms Dosage: How Much Do You Actually Need? Absorption: What Affects How Much You Use? Vitamin B6 and Zinc: Why They Appear in Formulas Side Effects and Safety What to Look for When Buying Magnesium PURETREX Magnesium Glycinate Complex Frequently Asked Questions
What Is Magnesium and Why Does It Matter?
Magnesium is the fourth most abundant mineral in the human body and is involved in over 300 enzymatic reactions. It is classified as an essential mineral, meaning the body cannot produce it and must obtain it from dietary or supplemental sources.
The adult human body contains approximately 25 grams of magnesium. Around 50–60% is stored in bone tissue, with most of the remainder in soft tissues such as muscle and organs. Less than 1% circulates in the blood — one reason why standard blood tests (serum magnesium) can be unreliable indicators of total body magnesium status.
Dietary sources include dark green leafy vegetables (spinach, kale, Swiss chard), nuts and seeds (pumpkin seeds, almonds, cashews), legumes (black beans, chickpeas), whole grains, dark chocolate, avocados, and some fatty fish. Despite the availability of magnesium-rich foods, dietary intake across the UK population frequently falls below recommended levels.
Magnesium is one of the few supplement ingredients with a strong set of authorised health claims in the UK — ten EFSA-evaluated claims covering everything from muscle function to tiredness reduction.
What Can Magnesium Legally Claim in the UK?
Unlike many supplement ingredients, magnesium has a robust set of authorised health claims on the GB Nutrition and Health Claims Register. These are the only claims that can legally be made:
✦ EFSA-Authorised Health Claims for Magnesium
- Magnesium contributes to a reduction of tiredness and fatigue
- Magnesium contributes to electrolyte balance
- Magnesium contributes to normal energy-yielding metabolism
- Magnesium contributes to normal functioning of the nervous system
- Magnesium contributes to normal muscle function
- Magnesium contributes to normal protein synthesis
- Magnesium contributes to normal psychological function
- Magnesium contributes to the maintenance of normal bones
- Magnesium contributes to the maintenance of normal teeth
- Magnesium has a role in the process of cell division
These claims require a product to provide at least 15% of the NRV (56.25mg) per serving. Any claim beyond this list — such as "magnesium cures anxiety" or "fixes insomnia" — is not authorised and is illegal in UK marketing. The authorised claims describe magnesium's contribution to normal bodily functions, not therapeutic effects.
Magnesium Deficiency: How Common Is It?
There are two distinct concepts to understand:
📊 Clinical Hypomagnesaemia
Severely low serum magnesium (below 0.7 mmol/L) is relatively uncommon in the general population. It is associated with specific medical conditions, medications (particularly proton pump inhibitors and certain diuretics), chronic alcoholism, and malabsorption disorders.
📉 Suboptimal Magnesium Intake
Far more prevalent. The UK National Diet and Nutrition Survey (NDNS) has consistently reported that a significant proportion of the population does not meet the Reference Nutrient Intake through diet alone. The RNI is 300mg/day for men and 270mg/day for women.
Groups at higher risk include older adults (absorption decreases with age), people consuming highly processed diets, athletes (magnesium lost through sweat), people taking certain medications, and individuals with digestive conditions affecting absorption.
Types of Magnesium: A Complete Comparison
Each form consists of elemental magnesium bonded to a different carrier molecule — and this carrier significantly affects absorption, bioavailability, and tolerability.
| Form | Carrier | Bioavailability | GI Tolerance | Best Known For |
|---|---|---|---|---|
| Glycinate (Bisglycinate) | Glycine (amino acid) | High | Excellent | Most popular premium form |
| Citrate | Citric acid | Good | Moderate (mild laxative) | Well-researched absorption |
| Malate | Malic acid | Good | Good | Energy metabolism (Krebs cycle) |
| Taurate | Taurine (amino acid) | Good | Good | Cardiovascular research |
| L-Threonate | Threonic acid (vit C metabolite) | Good | Good | Patented (Magtein®), most expensive |
| Orotate | Orotic acid | Moderate | Good | European clinical use |
| Oxide | Oxygen | Low | Poor (strong laxative) | Cheapest; high label numbers |
| Chloride | Chlorine | Moderate | Moderate | Oral and topical formats |
| Sulphate | Sulphur + oxygen | Low | Poor | Epsom salts (bath use only) |
When a product doesn't specify which form of magnesium it uses, it's likely using oxide — the cheapest form with the lowest bioavailability
Magnesium Glycinate (Bisglycinate): Why It Dominates the Market
High Bioavailability
Absorbed through amino acid transport pathways rather than competing with other minerals. Chelated forms consistently outperform inorganic forms in studies.
Minimal GI Side Effects
Unlike citrate, oxide, and sulphate, glycinate rarely causes loose stools — it doesn't draw water into the intestines the way osmotic forms do.
The Glycine Bonus
Glycine is an inhibitory neurotransmitter with its own research base. Taking magnesium glycinate delivers both magnesium and a meaningful dose of glycine.
Naming note: "Magnesium glycinate" and "magnesium bisglycinate" are the same compound. "Bisglycinate" is more chemically precise (two glycine molecules per magnesium atom). If a label says either, it's the same form.
Why Some Supplements Use Multiple Magnesium Forms
🔄 The Multi-Form Rationale
Different absorption pathways: Chelated forms (glycinate, taurate, malate) and ionic forms (citrate, chloride) are absorbed through different gut mechanisms. Multiple forms utilise multiple pathways simultaneously.
Different carrier benefits: Each carrier molecule (glycine, malic acid, taurine, citric acid) has its own properties — delivering magnesium alongside several beneficial organic compounds.
Reduced GI sensitivity: Spreading the dose across forms rather than loading a single one reduces the likelihood of osmotic laxative effects.
Dosage: How Much Magnesium Do You Actually Need?
300mg/day for men, 270mg/day for women. This is from ALL sources — food + supplements combined.
375mg/day. This is the labelling reference value used on supplement packaging in the UK.
250mg elemental magnesium per day from supplements specifically — on top of what you get from food.
"Magnesium Glycinate 500mg" = entire compound weight. Elemental magnesium is only ~14% of this. Always check the elemental figure on the label.
Most magnesium supplements provide 200–400mg elemental magnesium per daily serving, intended to top up dietary intake. Taking magnesium with food generally improves absorption and reduces GI side effects.
Absorption: What Affects How Much You Actually Use?
Taking a supplement is only half the equation — what matters is how much your body actually absorbs and utilises.
Form Matters
Chelated organic forms (glycinate, citrate, malate) are significantly better absorbed than inorganic forms (oxide, sulphate).
Dose Size
Absorption is inversely related to dose. Smaller, divided doses (100–150mg twice daily) absorb better than one large dose.
Vitamin D Status
Magnesium is needed for vitamin D activation. Low vitamin D status may reduce magnesium absorption efficiency.
Vitamin B6 has been shown to facilitate magnesium transport into cells — one reason it's frequently included in magnesium formulas. BioPerine® (piperine from black pepper) may enhance absorption by affecting intestinal permeability. Absorption inhibitors include high-dose calcium, zinc, or iron taken simultaneously, plus phytates and oxalates in food.
Vitamin B6 and Zinc: Why They Appear in Magnesium Formulas
✦ EFSA-Authorised Claims for Vitamin B6
- Vitamin B6 contributes to normal functioning of the nervous system
- Vitamin B6 contributes to normal psychological function
- Vitamin B6 contributes to normal energy-yielding metabolism
- Vitamin B6 contributes to the reduction of tiredness and fatigue
- Vitamin B6 contributes to the regulation of hormonal activity
✦ EFSA-Authorised Claims for Zinc
- Zinc contributes to normal functioning of the immune system
- Zinc contributes to maintenance of normal bones
- Zinc contributes to normal cognitive function
- Zinc contributes to normal fertility and reproduction
- Zinc contributes to the protection of cells from oxidative stress
Published research has examined the combination of magnesium with vitamin B6, particularly the French MAGNE-Stress study comparing magnesium alone vs magnesium + B6 in adults with low magnesium and high stress levels. Many people low in magnesium are also low in zinc — both minerals are depleted by similar dietary and lifestyle factors.
Side Effects and Safety
Magnesium is generally well-tolerated at standard supplemental doses, but there are important considerations:
⚠️ GI Effects (Most Common)
Loose stools or diarrhoea — dose-dependent and form-dependent. Oxide, citrate, and sulphate cause the most GI issues due to osmotic laxative effect. Glycinate, malate, and taurate are least likely to cause disturbance.
⚠️ Kidney Function
Individuals with impaired kidney function should exercise particular caution. The kidneys regulate blood magnesium levels, and impaired function can lead to accumulation. Anyone with chronic kidney disease should consult their doctor.
⚠️ Drug Interactions
Antibiotics (tetracyclines, quinolones): leave 2+ hours between doses. Bisphosphonates (osteoporosis drugs): same spacing. Magnesium may also affect absorption of certain blood pressure medications and thyroid hormones. Consult your doctor or pharmacist.
Pregnancy: Magnesium is generally considered safe during pregnancy and is sometimes recommended by healthcare professionals. Specific dosage should be discussed with a midwife or doctor.
What to Look for When Buying Magnesium in the UK
Quality Buying Checklist for Magnesium
- Elemental magnesium stated clearly — not just compound weight. 1,000mg magnesium glycinate ≠ 1,000mg magnesium
- Chelated forms prioritised — glycinate, malate, taurate, citrate over oxide, carbonate, sulphate
- Form specified on label — if not stated, likely oxide (cheapest, worst absorbed)
- Vitamin B6 + zinc at meaningful doses — at or above NRV for genuine complementary benefit
- BioPerine® for absorption — patented black pepper extract with published bioavailability data
- No proprietary blends — individual ingredient amounts should be disclosed
- Third-party tested — independent verification of purity, heavy metals, label accuracy
- UK manufactured under GMP — Food Standards Agency oversight
- Vegan capsules, no unnecessary fillers
PURETREX Magnesium Glycinate Complex
Magnesium Glycinate Complex — 6 Forms + Vitamin B6, Zinc & BioPerine®
- Magnesium Bisglycinate 30:1 — 300mg
- Magnesium Malate 25:1 — 250mg
- Magnesium Citrate 20:1 — 100mg
- Magnesium Taurate 15:1 — 100mg
- Magnesium L-Threonate 10:1 — 80mg
- Magnesium Orotate 10:1 — 60mg
- Vitamin B6 (P-5-P active form) — 20mg
- Zinc Picolinate 10:1 — 30mg
- BioPerine® 95% — 10mg
- 120 pullulan vegan capsules · 60 servings
📋 Combined Authorised Claims
Magnesium: Contributes to normal muscle function, normal energy-yielding metabolism, reduction of tiredness and fatigue, normal functioning of the nervous system, and normal psychological function.
Vitamin B6: Contributes to normal functioning of the nervous system, normal psychological function, reduction of tiredness and fatigue, and regulation of hormonal activity.
Zinc: Contributes to normal cognitive function, normal functioning of the immune system, and protection of cells from oxidative stress.
Ships same-day before 1PM Mon–Fri / 10AM Sat · Free UK delivery over £60
Frequently Asked Questions