Magnesium
Magnesium is an essential mineral the body uses in over 300 enzyme reactions — including muscle function, nerve signalling, and energy production. UK NHS reference intakes are 300 mg/day for men and 270 mg/day for women. Many UK adults fall short of those numbers in dietary surveys.
Camden Medicals editorial · Last reviewed 25 April 2026 · Next review April 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Mineral
- NHS daily RNI
- 300 mg ♂ · 270 mg ♀
- Typical supplemental
- 200–400 mg/day in supplemental form
- Top use evidence
- Strong
On this page
What it is
Magnesium is an alkaline-earth metal — element 12 on the periodic table — that forms the divalent Mg²⁺ ion in the body. The body holds around 25 g in total, with roughly 60% in bone and 25% in muscle. Blood concentration is tightly regulated by the kidneys, so a normal blood test does not rule out low total-body stores.
UK food sources include pumpkin seeds, almonds, cocoa, spinach, oats, and black beans. Most UK adults get the bulk of their magnesium from cereal products, dairy, and vegetables.
At a glance
- Required for muscle and nerve function, energy metabolism, and bone maintenance.
- UK NHS RNI: 300 mg/day (men), 270 mg/day (women).
- Different forms have very different absorption — bisglycinate, citrate, malate, taurate are well absorbed; oxide is poorly absorbed.
- Generally safe; loose stools at higher supplemental doses are the typical dose-limiter.
What people use it for
Adults whose UK dietary intake falls short of the NHS RNI
Topping up dietary magnesium toward the 300/270 mg RNI. [1]
Some evidenceStrongPeople taking long-term proton-pump inhibitors (PPIs)
Long-term PPI use is associated with reduced serum magnesium; the MHRA recommends monitoring magnesium status during long-term PPI therapy. Whether supplementation should be initiated is a clinical decision; discuss with your pharmacist or GP. [5]
Some evidenceLimitedPregnancy-related leg cramps
Cochrane evidence is conflicting in pregnancy-related cramps; some trials show benefit, others none. Discuss with a midwife or GP before starting. [3]
Some evidenceLimitedAdults eating a diet rich in seeds, leafy greens, and whole grains
Routine supplementation may be unnecessary — dietary intake is likely already adequate. [1]
Some evidenceModerate
How it works
Magnesium acts as a co-factor for ATP — every energy-using reaction in the cell requires Mg-ATP, not free ATP. It also gates the NMDA receptor in the brain and modulates the calcium channel in heart muscle, which is why early signs of low magnesium often appear as fatigue, cramps, and palpitations before a blood test changes.
Common myths
Myth"Magnesium fixes leg cramps"
RealityA 2020 Cochrane review found that magnesium probably does not reduce idiopathic skeletal-muscle cramps in older adults. It may help in pregnancy-related cramps. Many people try it because it is safe and cheap, not because the evidence supports it. [3]
Myth"Magnesium oxide is fine — it is 60% elemental magnesium"
RealityOxide does have a high elemental percentage per gram, but in absorption studies its bioavailability is around 4% (Firoz & Graber 2001). The bioavailable dose delivered is modest. It is widely used because it is the cheapest form. [6]
Myth"Higher milligrams on the label means a stronger product"
RealityThe compound mass on the label includes the carrier (e.g. glycine, citrate, oxide). Two products labelled "1,000 mg magnesium" can deliver very different amounts of elemental magnesium depending on which compound is used. Read the elemental amount, not the headline.
Common online questions
Synthesised from the questions UK shoppers most often ask online about Magnesium. Each answer is editorial and links to its evidence in the Sources list below.
Will magnesium help me sleep?
Some small randomised trials in older adults have reported modest improvements in self-reported sleep quality at 320–500 mg/day for a few weeks (Mah & Pitre 2021 meta-analysis). Evidence is mixed and trial quality varies. There is no GB-authorised health claim that magnesium aids sleep — that wording would be unauthorised on a UK label. If you sleep poorly, the higher-yield route is to check sleep-hygiene basics first and discuss persistent insomnia with your GP. [7]
Which magnesium form is best — bisglycinate, citrate, malate, taurate, or oxide?
For absorption, the named chelated forms (bisglycinate, citrate, malate, taurate) are well-absorbed; oxide is poorly absorbed (~4% bioavailability per Firoz & Graber 2001) and is best thought of as a cheap dose-padder. None of the well-absorbed forms is meaningfully different from the others on hard outcomes; preference often comes down to bowel tolerance (citrate is the most laxative; bisglycinate and taurate the gentlest). Read the elemental-magnesium amount on the label, not just the compound milligrams. [6]
Can magnesium help with anxiety or stress?
The GB-authorised health claim is that magnesium "contributes to normal psychological function" — a claim about adequacy supporting normal function, not a claim that supplementation treats anxiety. The ASA Sweet Bee Organics ruling specifically upheld a complaint against an "anxiety" claim on a magnesium supplement. If anxiety is affecting your day-to-day, talk to your GP about evidence-based treatments. [8]
Why does magnesium make me poop more (or give me diarrhoea)?
Magnesium that is not absorbed in the small intestine pulls water into the bowel by osmosis — this is why magnesium hydroxide and magnesium citrate are used as laxatives in clinical practice. At supplemental doses above ~400 mg/day, loose stools become the common dose-limiter. The fix is to lower the dose, split it across the day, or switch to a better-absorbed chelated form such as bisglycinate, which is gentler on the bowel.
Should I take magnesium with calcium, vitamin D, or zinc?
Magnesium is required as a co-factor in the body for converting vitamin D into its active form, so co-occurring adequacy makes biochemical sense. There is no clinical reason to dose them together at the same time of day; spacing them is fine. Avoid co-dosing magnesium with iron or with tetracycline / quinolone antibiotics in the same hour because both will reduce absorption of those medicines (separate by 2 hours).
Do I need to take magnesium if I eat well?
UK NHS dietary surveys show many adults fall short of the 300 mg (men) / 270 mg (women) Reference Nutrient Intake. If your diet is rich in seeds, leafy greens, oats, beans, and cocoa, you are likely to meet the RNI from food. Routine supplementation has the most upside for adults whose intake is low; for everyone else, the gain is marginal. [1]
Can I take too much magnesium?
The EU SCF set a Tolerable Upper Intake Level of 250 mg/day for magnesium added through supplements (this is in addition to magnesium from food). Above this, loose stools become more likely. Hypermagnesaemia (clinically high blood magnesium) is rare in healthy people and is mostly a concern in renal failure or with very large doses. The most useful cap for most adults is the dose at which your bowel tells you to stop.
⚖️ The official position
What may lawfully be claimed about Magnesium in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“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”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
10 authorised claims — show / hide
- "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"
Camden guides citing Magnesium
Editorial pieces from the Camden blog that reference Magnesium. Each guide cites the evidence it draws on.
Magnesium Glycinate vs Citrate vs Oxide: Which Form Actually Does What
April 2026
Read the guide →Glycemic Index and Glycemic Load: What They Mean for UK Shoppers
April 2026
Read the guide →Healthy and Unhealthy Sugars: Is Fruit Bad? (And Bananas?)
April 2026
Read the guide →Paracetamol vs Panadol: Why Generic Medicines Work Just as Well
April 2026
Read the guide →
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Idiopathic skeletal-muscle cramps (older adults)
LimitedEvidencelimitedA 2020 Cochrane review concluded "it is unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps". In the pregnancy- related cramp sub-group the literature is conflicting and trials could not be combined. [3]
Migraine prevention
ModerateEvidencemoderateAmerican Headache Society and American Academy of Neurology 2012 guidelines list magnesium as Level B for episodic migraine prevention. UK NICE migraine guidance (CG150) does not currently list magnesium. [9,10]
Type 2 diabetes — glycaemic control
LimitedEvidencelimitedMeta-analyses suggest a small reduction in HbA1c with magnesium supplementation in T2D populations. Not standard of care in UK NICE pathways (NG28 is silent on magnesium). [11,12]
Hypertension
LimitedEvidencelimitedMeta-analyses (Zhang 2016; Dibaba 2017) suggest modest blood-pressure reductions with supplementation, mostly in deficient or hypertensive subjects. Not a replacement for first-line antihypertensives. [13,14]
Sleep quality
LimitedEvidencelimitedMah & Pitre 2021 meta-analysis of older adults found small improvements in self-reported sleep quality. Evidence is mixed and trial quality varies. [7]
Safety
Magnesium is generally safe at typical supplemental doses (200–400 mg/day). The most common side effect at higher doses is loose stools, which reverses when you reduce the dose.
Talk to your pharmacist or GP first if you:
- You have severe kidney disease (CKD stage 4 or 5).
- You take levothyroxine, a tetracycline or quinolone antibiotic, or a bisphosphonate (separate magnesium from these by 2–4 hours).
- You take long-term proton-pump inhibitors (PPIs) — magnesium status can drift low over years; your pharmacist can advise on monitoring.
- You take digoxin — magnesium status matters for digoxin tolerance.
- You are pregnant, breastfeeding, or thinking of becoming pregnant.
Common side effects: Loose stools and mild stomach discomfort at supplemental doses above ~400 mg/day. Reverses when you reduce or stop.
Pregnancy and breastfeeding
The UK NHS RNI is not raised during pregnancy (270 mg/day). Supplemental magnesium at typical food-supplement doses is generally regarded as safe in pregnancy. As with any supplement, talk to your pharmacist, GP, or midwife before starting.
NHS RNI rises slightly to 320 mg/day during breastfeeding.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Severe renal impairment (CKD stage 4–5) — discuss with your pharmacist or GP before supplementing.
- Concurrent use of magnesium-containing medicines (some antacids).
Drug interactions
- Tetracycline antibiotics — separate doses by 2 hours.
- Quinolone antibiotics — separate doses by 2 hours.
- Bisphosphonates — separate doses by 2 hours.
- Levothyroxine — separate doses by 4 hours (chelation reduces thyroxine absorption; BNF Appendix 1).
- Long-term PPI use — may lower serum magnesium; monitor (MHRA Drug Safety Update).
- Digoxin — hypomagnesaemia potentiates digoxin toxicity; correct magnesium status (BNF Appendix 1).
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Loose stools at higher doses (the typical dose-limiter).
- Mild abdominal discomfort.
Rare side effects
- Hypermagnesaemia (mostly in renal failure or with very high doses).
How to take it
- UK Reference Nutrient Intake
- 300 mg/day (men) · 270 mg/day (women)
- Typical supplemental range
- 200–400 mg/day in supplemental form
- UK upper limit (supplemental)
- 250 mg/dayThe UL refers to magnesium added through supplements, not total intake including food. The IOM (US) figure of 350 mg is sometimes seen — it is the US value, not the UK or EU value.
- Timing
- Anytime — split doses if higher amounts are taken.
How to spot quality
Look for
- Named, organic-acid form: bisglycinate (also called glycinate), citrate, malate, taurate, threonate.
- Elemental magnesium amount stated alongside compound mass (e.g. "375 mg elemental magnesium").
- Per-form milligram breakdown when blends are used.
- GMP-certified manufacture; ideally third-party heavy-metals testing.
Red flags
- Magnesium oxide alone (high elemental percentage but low bioavailability).
- High milligram figure with no compound or elemental amount specified.
- Magnesium "complex" or "blend" with no per-form breakdown.
- Form simply listed as "magnesium" with no compound named.
Where Camden lands · meets the bar
Camden's NB-500 declares 180 mg magnesium bisglycinate, 165 mg malate, and 30 mg taurine chelate per three-capsule serving — providing 375 mg elemental magnesium (100% NRV). The forms are named with their individual milligram amounts; manufacture is GMP-certified through Troo Health Care.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Vitamin D3
Moderate evidenceMagnesium is the cofactor that activates vitamin D — without enough, D3 supplements work less well.
Every step of vitamin D metabolism — from skin synthesis through liver 25-hydroxylation (CYP27A1) and kidney 1-alpha-hydroxylation (CYP27B1) to D-binding-protein transport and receptor activation — requires magnesium-dependent enzymes or ATP–magnesium complexes. Adults with low magnesium intake show a blunted serum 25-OH-D response to D3 supplementation. The relationship is co-factor dependence, not synergy in the classical sense — adequate magnesium does not enhance D3 beyond normal function; insufficient magnesium impairs it.
Evidence: Uwitonze & Razzaque 2018 (J Am Osteopath Assoc) reviews the cofactor relationship and the magnesium dependence of vitamin D activation. [15,16]
Doses studied: Co-occurring adequacy: 300–375 mg magnesium with 10 µg (400 IU) D3 daily (UK RNI for both)
Vitamin B6
Moderate evidenceB6 helps move magnesium into cells — the combination is the most-studied pairing for PMS and migraine.
Vitamin B6 (pyridoxal-5-phosphate) facilitates the cellular uptake and intracellular retention of magnesium ions, particularly in erythrocytes and neuronal tissue. The combination is the single most-studied micronutrient pairing for premenstrual syndrome symptoms, with smaller bodies of evidence for migraine prophylaxis. Mechanistic plausibility is strong; trial quality is heterogeneous.
Evidence: Walker 1998 (J Womens Health Gend Based Med) RCT on Mg+B6 vs Mg alone for PMS. De Souza 2000 (J Womens Health Gend Based Med) extended this. Cochrane reviews of either nutrient alone for PMS show modest, mixed effect; combination data is more positive but from smaller studies. [17,18]
Doses studied: 200–400 mg magnesium with 50 mg vitamin B6 daily (B6 dose well below the 100 mg/day chronic-neuropathy threshold)
Calcium (Ca)
Moderate evidenceCalcium-magnesium balance is fundamental to bone, muscle, and neuromuscular function — magnesium is also a cofactor for parathyroid hormone secretion and calcitriol activation.
Magnesium is required as a cofactor for parathyroid hormone (PTH) secretion and the conversion of 25-OH-D to active 1,25-(OH)₂-D (calcitriol). Severe magnesium deficiency therefore impairs the regulated component of calcium absorption — a magnesium-deficient adult cannot fully use a calcium supplement until magnesium status is restored. Calcium and magnesium also act as physiological antagonists at smooth muscle (calcium drives contraction; magnesium drives relaxation), the basis for the calcium-magnesium muscle-cramp framing — though trial evidence for routine combined supplementation in muscle cramp is limited. At standard supplement doses (400–500 mg calcium + 200–300 mg magnesium per serving) competition for divalent-cation transporters is not clinically significant.
Evidence: Magnesium-PTH and magnesium-calcitriol mechanisms well established. UK Article 13.1 claim "Magnesium contributes to the maintenance of normal bones" supports the pairing on a regulatory basis. Trial evidence for combined calcium-magnesium supplementation on hard endpoints (fracture, cramp resolution) is limited. [8]
Doses studied: 500–1000 mg calcium with 200–400 mg magnesium daily; magnesium glycinate or bisglycinate is the gentlest gut-tolerated form when stacked with calcium carbonate
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules
L-Theanine
Limited evidenceSleep + relaxation cluster — magnesium NMDA / GABA-A modulation alongside l-theanine glutamatergic calm.
Magnesium is a voltage-dependent NMDA-receptor antagonist (the magnesium block of the channel pore is tonically active at resting membrane potential) and modulates GABA-A receptor function as a positive allosteric effector. L-theanine is an NMDA antagonist with separate alpha-wave EEG signal in relaxation studies. The two mechanisms are complementary on the glutamatergic-GABAergic relaxation axis. Both are commonly stacked in evening unwind formulas.
Evidence: UK Article 13.1 magnesium psychological-function claim authorised. L-theanine has no UK authorised claim; the combination has not been directly trialled. [8]
Doses studied: 100–200 mg l-theanine with 200–400 mg magnesium glycinate, evening dose
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules
Valerian (Valeriana officinalis)
Limited evidenceSleep-cluster mineral partner — magnesium GABAergic and NMDA modulation alongside valerian's GABA-A axis.
Magnesium is a cofactor for over 300 enzymatic reactions and a physiological NMDA-receptor antagonist (voltage-dependent block of the channel pore at resting membrane potential). Magnesium also modulates GABA-A receptor function through positive allosteric effects. Valerian is a UK THR-registered traditional herbal sleep aid acting primarily on the GABA-A axis. The combination is mechanism-additive across different facets of GABAergic and glutamatergic signalling. In human trials magnesium glycinate or bisglycinate at 200–400 mg evening has shown modest sleep-quality effects; the combination with valerian has not been directly trialled.
Evidence: Magnesium-NMDA-GABA mechanism well established; trial evidence for magnesium alone on sleep is modest. UK Article 13.1 magnesium psychological-function claim authorised. [8]
Doses studied: Valerian 300–600 mg with magnesium glycinate or bisglycinate 200–400 mg, evening dose
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules
Tart Cherry (Montmorency)
Limited evidenceSleep-cluster pairing — magnesium GABAergic relaxation alongside tart cherry melatonin / anti-inflammatory anthocyanins.
Magnesium provides GABA-A allosteric modulation and NMDA blockade at resting potential. Tart cherry (Prunus cerasus, Montmorency variety) carries small quantities of melatonin plus tryptophan and anti-inflammatory anthocyanins. The combination addresses different facets of the sleep-onset axis (magnesium's neuromuscular relaxation; tart cherry's circadian and recovery contribution) and is commonly stacked in evening sleep formulas.
Evidence: UK Article 13.1 magnesium psychological-function claim. Tart cherry sleep evidence is modest (small RCTs in older adults). The combination has not been directly trialled. [8]
Doses studied: 1500 mg tart-cherry concentrate with 200–400 mg magnesium glycinate, evening dose
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules
Creatine
Moderate evidenceEnergy + recovery cluster — creatine ATP-buffering meets magnesium as the obligate Mg-ATP cofactor for kinases.
Creatine phosphate is the body's short-term ATP-buffer system via creatine kinase (CK). All ATP-using enzymes act on the Mg-ATP complex; magnesium is therefore a stoichiometric cofactor for the phosphoryl transfer that creatine drives. The combination is mechanism-complementary on the energy-metabolism axis. A subset of marketed products use magnesium-creatine chelate forms; the evidence basis for chelated forms above creatine monohydrate is limited.
Evidence: Magnesium-ATP biochemistry textbook. UK Article 13.1 creatine performance claim authorised at 3 g/day. UK Article 13.1 magnesium claims for muscle function and energy-yielding metabolism authorised. [8]
Doses studied: 3 g/day creatine monohydrate with 200–400 mg magnesium daily
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules · Purifera™ Creatine Monohydrate Powder 500g (200 mesh micronised)
L-Tryptophan
Limited evidenceSleep-cluster pairing — magnesium relaxation alongside l-tryptophan as the serotonin / melatonin substrate.
L-tryptophan is the dietary precursor for 5-HTP, serotonin and melatonin via tryptophan hydroxylase (rate-limiting) and aromatic L-amino acid decarboxylase. Magnesium provides GABA-A allosteric modulation and neuromuscular relaxation. The pairing addresses two facets of sleep architecture — substrate availability for evening melatonin synthesis and relaxation tone via magnesium. Note the historical 1989 EMS contamination incident: pharmaceutical-grade tryptophan with documented manufacturing chain is required.
Evidence: UK Article 13.1 magnesium psychological-function claim authorised. L-tryptophan has no UK authorised claim and the EMS history demands supplier-chain discipline. [8]
Doses studied: 500–1000 mg l-tryptophan with 200–400 mg magnesium glycinate, evening dose
Found in Camden: Aurifera™ Magnesium Complex 120 Capsules
Alpha Lipoic Acid (ALA / thioctic acid)
Limited evidenceMitochondrial-cluster pairing — ALA mitochondrial-cofactor + magnesium ATP-Mg energy-metabolism cofactor.
ALA cofactor for pyruvate dehydrogenase + α-ketoglutarate dehydrogenase mitochondrial enzymes; magnesium cofactor for ATP-bound enzymes throughout energy metabolism.
Evidence: UK Article 13.1 magnesium energy-metabolism claim. [8]
Doses studied: 300-600 mg ALA + 200-400 mg magnesium daily.
Vitamin B1 (Thiamine)
Moderate evidenceEnergy-metabolism cluster — B1 PDH + αKGDH cofactor + magnesium ATP-binding cofactor.
B1 enzyme cofactor; magnesium ATP-Mg cofactor in same energy-metabolism reactions. UK Article 13.1 energy-metabolism + psychological-function claims for both.
Evidence: UK Article 13.1 claims authorised. [8]
Doses studied: 1.4 mg B1 + 200-400 mg magnesium daily.
Vitamin B2 (Riboflavin)
Moderate evidenceEnergy-metabolism pair.
B2 redox cofactor + magnesium ATP cofactor. Mechanism complementary.
Evidence: UK Article 13.1 claims authorised. [8]
Doses studied: 1.4 mg B2 + 200-400 mg magnesium daily.
Vitamin B5 (Pantothenic Acid)
Moderate evidenceEnergy / mental-performance cluster.
B5 mental-performance UK Article 13.1 + magnesium psychological-function UK Article 13.1.
Evidence: UK Article 13.1 claims both. [8]
Doses studied: 6 mg B5 + 200-400 mg magnesium daily.