MagnesiumMineral

• Correcting a documented magnesium deficiencyLikely helps

  This is the one use nobody argues about. Gröber and Kisters' 2017 review in Nutrients describes oral magnesium's effectiveness for magnesium deficiency as 'beyond controversy' [7].
  
  That is a different claim from everything below, which is about supplementing people who are not deficient. ^[7]

• Muscle cramps in older adultsNot shown to help

  A 2020 Cochrane systematic review of 11 RCTs (735 participants) concluded it is unlikely magnesium delivers a clinically meaningful reduction in idiopathic cramps in older adults [3].
  
  For pregnancy-associated leg cramps the evidence is conflicting rather than negative [3].
  
  For exercise- or disease-associated cramps there isn't enough reliable evidence to judge at all [3]. ^[3]

• Blood pressurePossibly helps

  A Cochrane review of 12 trials in 545 hypertensive people found a small diastolic reduction of about 2.2 mmHg [1].
  
  A separate meta-analysis of 22 studies found roughly 3–4 mmHg systolic and 2–3 mmHg diastolic, somewhat larger above 370 mg/day [1].
  
  The FDA approved a qualified health claim in 2022 while stating in the same document that the evidence is 'inconsistent and inconclusive' [1].
  
  A 2025 review in the American Heart Association's Hypertension notes magnesium may add to antihypertensive medication's effect, via vasodilation and renin-angiotensin-aldosterone inhibition [13]. That is a proposed mechanism, not a settled outcome.
  
  ⚠ Worth naming: across all of these outcomes the government sources — NIH ODS, Cochrane, the FDA — read the evidence far more cautiously than supplement marketing does [1]. ^[1]

• Glycemic control in type 2 diabetesPossibly helps

  Two literatures point different ways, and NIH ODS flags the split itself [1].
  
  Large prospective cohorts consistently link higher dietary magnesium to lower diabetes risk — a 7-cohort meta-analysis of 286,668 people found about 15% lower risk per 100 mg/day of intake [1].
  
  Small trials of magnesium supplements in people who already have diabetes have given conflicting results [1].
  
  The American Diabetes Association does not consider the evidence sufficient to recommend magnesium for glycemic control [1]. ^[1]

• Migraine frequencyPossibly helps

  Low serum and tissue magnesium is associated with migraine, and 3 of 4 small placebo-controlled trials found modest reductions in frequency at up to 600 mg/day [1].
  
  The American Academy of Neurology and American Headache Society concluded magnesium is 'probably effective' for migraine prevention [1].
  
  ⚠ The catch is arithmetic. The effective dose typically exceeds the 350 mg/day supplemental limit, so this belongs under medical supervision [1]. ^[1]

• Bone mineral densityPossibly helps

  Observational studies link higher magnesium intake to higher bone mineral density [1].
  
  One small 30-day trial gave postmenopausal women with osteoporosis 290 mg/day of elemental magnesium as citrate and found suppressed bone turnover versus placebo [1].
  
  Thirty days and one small trial is not a conclusion, and NIH ODS says as much [1]. ^[1]

• Loss of appetite, nausea, vomiting, fatigue and weakness — the early, nonspecific stage
• Numbness, tingling, muscle cramps, contractions and tremor, as neuromuscular excitability rises
• Seizures, personality changes and abnormal heart rhythms including coronary spasm, in more severe cases
• Low blood calcium or low blood potassium, since severe depletion disrupts both
• Hypomagnesemia is defined as serum magnesium below 0.75 mmol/L; the normal range is 0.75–0.95 mmol/L
• True dietary deficiency is uncommon in healthy people — the kidneys sharply limit urinary loss when intake drops
• Higher risk of inadequacy: malabsorptive gut disease such as Crohn's or celiac, type 2 diabetes, chronic alcoholism, and older age
• ⚠ A broader academic table (Gröber and Kisters, 2017) adds anxiety, depression, headache, irritability and sleep disturbance [7]
• That wider list draws on a more heterogeneous evidence base than NIH's core, clinically established one [7]^[1]

• Magnesium oxideCheap bulk magnesium, and little else.

  Elemental content

  Inorganic salt of magnesium and oxygen. The reviewed sources rank it by absorption rather than by an elemental percentage [1].

  Absorption

  NIH ODS places oxide among the least well absorbed common forms, alongside magnesium sulfate [1].
  
  Pardo and colleagues' 2021 systematic review reaches the same general conclusion: organic forms outperform inorganic ones such as oxide [5].

  Best for

  Cheap bulk magnesium, and little else. It is also one of the forms most often linked to diarrhea [1].

• Magnesium citrateGeneral repletion, and the form pharmacist sources name for a calming effect .

  Elemental content

  Organic salt of magnesium and citric acid. Also sold in its own right as a laxative drug product [10].

  Absorption

  NIH ODS lists citrate among the better-absorbed forms, based on small studies [1].
  
  The percentage absorbed falls as the dose rises, per Pardo and colleagues' 2021 systematic review [5].

  Best for

  General repletion, and the form pharmacist sources name for a calming effect [8]. Splitting the dose works with its dose-dependent absorption rather than against it [5].

• Magnesium glycinateThe form most often recommended for sleep and anxiety.

  Elemental content

  Magnesium bound to the amino acid glycine — an organic form.

  Absorption

  It has a distinct route: uptake via the body's dipeptide transporter, not only as a free ion [5].
  
  That may be part of why it is usually easy on the gut [5].

  Best for

  The form most often recommended for sleep and anxiety. That is a widely repeated inference from glycine's own role, not a head-to-head trial result [5].

• Magnesium tauratePeople chasing absorption on the newest evidence.

  Elemental content

  Magnesium bound to the amino acid taurine — an organic form.

  Absorption

  Pardo and colleagues' 2021 review found taurate among the most bioavailable salts studied [5].
  
  The underlying studies used inconsistent methods, so they are genuinely hard to compare directly [5].

  Best for

  People chasing absorption on the newest evidence. ⚠ NIH ODS's own list names aspartate, citrate, lactate and chloride instead — the two sources agree organic beats inorganic but not on a single best form [1].

• Magnesium L-threonate (Magtein)The brain-targeted pitch, and the one with a funding problem.

  Elemental content

  Magnesium bound to L-threonic acid. It delivers relatively little elemental magnesium per dose [5].

  Absorption

  MIT-affiliated 2010 animal work found it uniquely raised magnesium in cerebrospinal fluid [5].
  
  A 2022 trial in 109 adults at 2 g/day for 30 days reported better memory scores versus placebo [6].

  Best for

  The brain-targeted pitch, and the one with a funding problem. ⚠ That human trial was funded directly by Wu-xi Magtein Bioscience, which markets the patented ingredient, despite a formal no-competing-interest declaration [6].
  
  It also costs substantially more than citrate or glycinate per unit of elemental magnesium [5].

• Magnesium chloride, lactate and aspartateReasonable general-purpose choices.

  Elemental content

  Chloride is an inorganic salt; lactate and aspartate are organic salts.

  Absorption

  NIH ODS's small-study evidence names aspartate, citrate, lactate and chloride as better absorbed than oxide or sulfate [1].
  
  Pardo and colleagues' 2021 review frames the same pattern more broadly, as organic beating inorganic [5].

  Best for

  Reasonable general-purpose choices. Note chloride also appears on NIH's list of forms most often implicated in diarrhea, alongside carbonate, gluconate and oxide [1].

• Magnesium hydroxide (milk of magnesia)Its labelled purpose. This is the category where documented magnesium toxicity actually comes from .

  Elemental content

  Inorganic salt sold mainly as an antacid and laxative drug product [11].

  Absorption

  MedlinePlus documents it as a medicine, not as a way to correct magnesium status [11].
  
  NIH's toxicity data attach specifically to very large doses of magnesium-containing laxatives and antacids [1].

  Best for

  Its labelled purpose. This is the category where documented magnesium toxicity actually comes from [1].

• Diarrhea, nausea and abdominal cramping

  High supplemental or medicinal doses commonly cause these, through an osmotic pull of water into the gut [1].
  
  Carbonate, chloride, gluconate and oxide are the forms most often implicated [1]. ^[1]

• Impaired kidney function

  The kidneys are the main route for clearing excess magnesium, so toxicity risk rises sharply with kidney impairment or failure [1].
  
  Documented toxicity follows very large doses of magnesium-containing laxatives or antacids, above roughly 5,000 mg/day [1].
  
  Symptoms run from low blood pressure, flushing and nausea to muscle weakness, breathing difficulty, irregular heartbeat and, in a few reported cases, cardiac arrest [1]. ^[1]

• Tetracycline and quinolone antibiotics

  Doxycycline, ciprofloxacin and levofloxacin can form insoluble complexes with magnesium, so less of each is absorbed [1].
  
  NIH ODS's spacing rule: take the antibiotic at least 2 hours before, or 4–6 hours after, a magnesium-containing supplement [1]. ^[1]

• Oral bisphosphonates

  Alendronate and other oral bisphosphonates for osteoporosis are absorbed less well when taken close to magnesium [1].
  
  Separating the two doses by at least 2 hours minimizes it [1]. ^[1]

• Diuretics — direction depends on the class

  Loop diuretics (furosemide, bumetanide) and thiazides (hydrochlorothiazide) increase urinary magnesium loss and can deplete you over time [1].
  
  Potassium-sparing diuretics (amiloride, spironolactone) do the opposite, reducing excretion — supplementing on top raises the risk of excess [1]. ^[1]

• Long-term proton pump inhibitors

  Use beyond about a year — esomeprazole, lansoprazole and the rest — can cause hypomagnesemia [1].
  
  The FDA advises checking serum magnesium before starting long-term PPI therapy and periodically afterward [1].
  
  In about 25% of FDA-reviewed cases, magnesium supplements did not correct the deficiency and the PPI had to be stopped [1]. ^[1]

• Very high-dose zinc

  Supplemental zinc at 142 mg/day, in the study NIH ODS cites, interfered with magnesium absorption and balance [1]. ^[1]

Magnesium sits across plant foods — green leafy vegetables, legumes, nuts, seeds and whole grains, plus some fortified cereals [1].

Only about 30–40% of dietary magnesium is actually absorbed [1].

Per USDA FoodData Central figures compiled by NIH ODS: pumpkin seeds 156 mg per ounce (37% DV), chia seeds 111 mg/oz, almonds 80 mg/oz [1].

Boiled spinach gives 78 mg per half cup, cashews 74 mg/oz, black beans 60 mg per half cup, edamame 50 mg per half cup [1].

Smaller amounts: a banana 32 mg, a cup of milk 27 mg, 3 oz of salmon 26 mg, a slice of whole-wheat bread 23 mg [1].

Refining grains strips out the magnesium-rich germ and bran, so white flour carries substantially less [1].

Cooking method matters too. A Heliyon-published analysis of six commonly eaten vegetables found boiled samples significantly lower in magnesium than raw ones, consistent with leaching into the water [14].

A medically reviewed nutrition explainer suggests steaming or microwaving with minimal water, and reusing the cooking liquid in soups or sauces [15].

No government or clinical guideline sets a best time of day. NIH's fact sheets don't address timing at all [1].

Regularity matters far more than the hour — magnesium's documented effects on blood pressure and migraine come from weeks of sustained use [8].

Pharmacist-reviewed guidance suggests evening dosing, about an hour before bed, when the goal is sleep or relaxation, commonly with glycinate or citrate [8].

Morning or split dosing suits people avoiding drowsiness. Citrate taken for its laxative effect is better kept well away from bedtime [8].

⚠ A real trade-off, unresolved. Practical sources say take magnesium with food for gut comfort [8].

Pardo and colleagues' 2021 systematic review notes net absorption may be somewhat higher on an empty stomach [5]. Neither is simply correct — one optimizes tolerability, the other absorption.

Spacing beats timing. Keep magnesium at least 2 hours away from bisphosphonates, tetracycline and quinolone antibiotics, and gabapentin, whatever hour you take it [8].