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Extra Strength Magnesium 400 mg

4.0
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(545 ratings)
Magnesium 400 mg
Product Image
Score72
A convenient 400 mg softgel is undermined by low-absorption magnesium oxide and a substantial risk of digestive upset.
How scoring works
Softgel
Quantity:60 Softgel(s) • (60 servings)
Goals:
Energy
Heart Health
Stress Relief
Cardiovascular Support
General Health

Score 72

A convenient 400 mg softgel is undermined by low-absorption magnesium oxide and a substantial risk of digestive upset.
How scoring works
$11.78($0.19 per serving)
Vitacost
$ 12.99
iHerb
$ 13.04
Walmart
$ 11.78
iHerb
$ 13.04
Report prices

Analysis

A 400 mg serving provides substantial magnesium, but all of it comes from magnesium oxide. The form is more likely to remain in the gut and produce laxative effects than deliver efficient systemic uptake.

Softgel delivery may be easy to swallow and includes a small amount of fat. Unlike fat-soluble nutrients, magnesium does not gain a clear absorption advantage from that lipid content.

It may fit people who tolerate oxide and value softgels. Users seeking absorbed magnesium for routine nutritional support have stronger options in citrate, glycinate, or malate.

Who is it for
  • Adults who prefer softgels
  • People who tolerate magnesium oxide
  • Users prioritizing a clearly stated high amount
Best for
  • One-softgel convenience
  • Budget magnesium use
  • Bowel-support effects

Pros

  • Provides 400 mg elemental magnesium
  • Easy-to-swallow softgel format
  • Clearly identifies the oxide form
  • Modest serving cost

Cons

  • Oxide has low systemic absorption
  • 400 mg may be difficult to tolerate
  • Added fat offers little magnesium benefit
  • Poor fit for efficient repletion

Warnings

  • The 400 mg oxide serving of supplemental magnesium may cause loose stools, cramping, or nausea; a smaller divided amount may be easier to tolerate.
  • Magnesium can reduce absorption of tetracycline or quinolone antibiotics; follow the prescriber or pharmacist’s spacing instructions.
  • Magnesium can interfere with levothyroxine absorption and should be separated according to medication guidance.
  • People with significantly reduced kidney function can accumulate magnesium and need clinician-guided use.

Nutrient quality

68 High impact

Magnesium oxide has weak systemic absorption despite the softgel format. The elemental amount reaches a substantial daily supplemental level, while the large oxide amount may cause diarrhea or stomach discomfort in sensitive users.

Ingredient transparency

80 Highest impact

The oxide form and elemental amount are clear, while inactive softgel ingredients are not supplied. Serving totals are apparent, but full directions and inactive ingredients are not supplied.

Customer satisfaction

56 Moderate impact

The supplied average rating is mixed. A substantial rating base gives the average reasonable reliability, while complaint and firsthand experience details are unavailable.

Value for money

79 High impact

Formula quality provides partial support for the asking position. The serving value is reasonably competitive within the category.

Report analysis

Goals

Energy
Energy
Impact
High effect
B+ Goal FitC Strength of SupportD CoverageA- Formula Quality
Magnesium · 400 mg

Magnesium is required for ATP-dependent enzymes and can improve energy when inadequate intake contributes to fatigue. The 400 mg amount is substantial and clearly disclosed.

Magnesium oxide has low systemic absorption, so the labeled amount overstates the likely absorbed contribution compared with glycinate, citrate, or malate. The dose and oxide form may also cause diarrhea or abdominal discomfort in sensitive users.

Study evidence
Magnesium Supportive 4 studies
Heart Health
Heart Health
Impact
High effect
A- Goal FitC- Strength of SupportD- CoverageA Formula Quality
Magnesium · 400 mg

Magnesium has a direct role in heart rhythm, vascular tone, and many energy-dependent reactions. The 400 mg amount is substantial, but magnesium oxide has poor systemic absorption compared with citrate or chelated forms.

A single-mineral design keeps the formula focused but limits coverage to one foundational pathway. The large oxide serving can cause diarrhea or stomach discomfort because much of it may remain in the digestive tract.

Study evidence
Magnesium Supportive 158 studies
Stress Relief
Stress Relief
Impact
High effect
B Goal FitC Strength of SupportC- CoverageB+ Formula Quality
Magnesium · 400 mg

Magnesium is relevant to nervous system regulation, but the oxide form limits its usefulness for systemic stress support. The single mineral also lacks adaptogenic or direct calming neurotransmitter coverage.

The amount is clearly disclosed and substantial, yet low absorption reduces the likely contribution. Magnesium oxide at this level may cause diarrhea or stomach discomfort in sensitive users.

Study evidence
Magnesium Supportive 13 studies
Cardiovascular Support
Cardiovascular Support
Impact
High effect
B Goal FitC- Strength of SupportD+ CoverageA Formula Quality
Magnesium · 400 mg

Magnesium supports vascular relaxation and normal electrical rhythm, giving this focused supplement a clear cardiovascular role. Magnesium oxide has low systemic absorption despite the high elemental amount.

The single-mineral approach does not address lipids, endothelial nitric oxide, or antioxidant protection. The oxide form at 400 mg may cause diarrhea or stomach discomfort in sensitive users.

Study evidence
Magnesium Supportive 123 studies
General Health
General Health
Impact
High effect
A Goal FitD+ Strength of SupportD CoverageB+ Formula Quality
Magnesium · 400 mg

Magnesium is a foundational mineral needed for energy metabolism, nerve signaling, and muscle function. The elemental amount is clearly disclosed and substantial.

Magnesium oxide has weak systemic absorption and is more likely than better organic forms to cause diarrhea or stomach discomfort. The formula therefore fits occasional laxative-like effects better than users seeking reliably absorbed magnesium support.

Study evidence
Magnesium Supportive 114 studies
Digestive Health
Digestive Health
Impact
Moderate effect
C Goal FitC+ Strength of SupportF CoverageA- Formula Quality
Magnesium · 400 mg

Magnesium oxide can draw water into the bowel, so it may help occasional constipation. Its low absorption and substantial dose also make loose stools, cramping, or stomach discomfort more likely.

The single-pathway formula does not support enzymes, the gut lining, the microbiome, or fiber intake. Clear dosing is useful, but the oxide form is a blunt motility option rather than broad digestive support.

Study evidence
Magnesium Supportive 50 studies
Testosterone Support
Testosterone Support
Impact
Moderate effect
D+ Goal FitD Strength of SupportF CoverageA Formula Quality
Magnesium · 400 mg

Magnesium is a foundational mineral with a possible role in maintaining bioavailable testosterone, especially when magnesium status is low. The disclosed elemental amount is substantial.

Magnesium oxide has low systemic absorption, which limits confidence in endocrine effects despite the high label amount. The substantial oxide dose may also cause diarrhea or stomach discomfort in sensitive users.

Study evidence
Magnesium Disputed 5 studies

Ingredients

IngredientAmount per serving
Calories
10 Calorie(s)
Total Fat
0.5 Gram(s)
Magnesium (Magnesium Oxide)
 400 mg
Gluten Free Adults 18–50
Report overview
Magnesium (Magnesium Oxide) · 400 mg OverallScore52
F Active Ingredient Quality & BioavailabilityA Dose, Safety & Label TransparencyD+ Value

The elemental magnesium amount is clearly disclosed and falls within the targeted daily range. Magnesium oxide has low systemic absorption and lacks patented chelation, limiting its fit for users seeking absorbed magnesium. Its below-median cost helps value, but the oxide form and substantial dose may cause diarrhea or stomach discomfort in sensitive users.

View ingredientView products
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91 Performance

Krebs Magnesium Potassium Complex

Nature's Way
<p>Magnesium lysinate and malate provide favorable forms at a useful amount, with a modest potassium contribution. Compared with the original, its magnesium form, dose clarity, and focused design offer a stronger quality-oriented option.</p>
88 Performance

Magnesium Bisglycinate Powder

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<p>Magnesium bisglycinate supplies a well-absorbed form at a practical, moderate amount. Compared with the original, its magnesium form, dose clarity, and focused design offer a stronger quality-oriented option.</p>
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Cal/Mag 500 mg/250 mg

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<p>Chelated calcium and magnesium provide a focused, balanced mineral formula with strong form quality. Compared with the original, its magnesium form, dose clarity, and focused design offer a stronger quality-oriented option.</p>
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Magnesium Bisglycinate Chelate

Healthy Origins
<p>TRAACS magnesium bisglycinate provides high-quality absorption quality, a useful elemental amount, and strong serving value in a clean powder. Its lower supplied serving cost makes it a more economical magnesium option than the original.</p>
83 Budget

Magnesium Citrate Pure Powder

Best Naturals
<p>A well-aligned amount of magnesium citrate delivers useful absorption in a focused powder. Its lower supplied serving cost makes it a more economical magnesium option than the original.</p>
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Magnesium Citrate 420 mg

Nutricost
<p>A substantial amount of magnesium citrate offers useful absorption and a focused formula. Its lower supplied serving cost makes it a more economical magnesium option than the original.</p>
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Magnesium Citrate 200 mg

Best Naturals
<p>A substantial amount of magnesium citrate combines useful absorption with a focused single-active design. Its stated magnesium form, practical dose, and lower serving cost offer a stronger balance of quality and value than the original.</p>
84 Value

Potassium + Magnesium

Nutricost
<p>A meaningful magnesium citrate amount anchors a simple two-mineral electrolyte formula. Its stated magnesium form, practical dose, and lower serving cost offer a stronger balance of quality and value than the original.</p>
80 Value

Magnesium Caps 500 mg

Life Extension
<p>Citrate, succinate, and a named glycinate chelate strengthen a multi-form magnesium blend, while oxide lowers average absorption. Its stated magnesium form, practical dose, and lower serving cost offer a stronger balance of quality and value than the original.</p>
Report alternatives

Sources

Published studies used for the product analysis and the top-ranked studies for each ingredient and goal.

  1. The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials.
    van der Schoot A; Creedon A; Whelan K; Dimidi E · Neurogastroenterology and motility · 2023
    Meta-analysis787 participants8 studies pooledDigestive Health forMagnesium
  2. A Randomized Double-blind Placebo-controlled Trial on the Effect of Magnesium Oxide in Patients With Chronic Constipation.
    Mori S; Tomita T; Fujimura K; Asano H; Ogawa T; Yamasaki T; Kondo T; Kono T; Tozawa K; Oshima T; Fukui H; Kimura T; Watari J; Miwa H · Journal of neurogastroenterology and motility · 2022
    Randomized trial34 participantsDigestive Health forMagnesium
  3. Diagnosis of magnesium-induced diarrhea.
    Fine KD; Santa Ana CA; Fordtran JS · The New England journal of medicine · 1991
    Clinical trial19 participantsDigestive Health forMagnesium
  4. Lactobacillus casei rhamnosus Lcr35 in children with chronic constipation.
    Bu LN; Chang MH; Ni YH; Chen HL; Cheng CC · Pediatrics international : official journal of the Japan Pediatric Society · 2007
    Randomized trial45 participantsDigestive Health forMagnesium
  5. Lactobacillus reuteri DSM 17938 and Magnesium Oxide in Children with Functional Chronic Constipation: A Double-Blind and Randomized Clinical Trial.
    Kubota M; Ito K; Tomimoto K; Kanazaki M; Tsukiyama K; Kubota A; Kuroki H; Fujita M; Vandenplas Y · Nutrients · 2020
    Randomized trial60 participantsDigestive Health forMagnesium
  6. Efficacy of oral magnesium therapy in the treatment of chronic constipation in spastic cerebral palsy children: a randomized controlled trial.
    Hassanein SMA; Deifallah SM; Bastawy HA · World journal of pediatrics : WJP · 2021
    Randomized trial100 participantsDigestive Health forMagnesium
  7. Magnesium-Rich Mineral Water Improves Stool Consistency and Bowel Habits in Healthy Subjects: A Randomized Controlled Trial.
    Yoneda H; Tomita T; Kitano T; Morishita D; Kodani M; Nishii N; Sei H; Eda H; Sato T; Kawai M; Yokoyama Y; Igeta M; Okugawa T; Fukui H; Shinzaki S · Neurogastroenterology and motility · 2026
    Randomized trial40 participantsDigestive Health forMagnesium
  8. Ca:Mg ratio, medium-chain fatty acids, and the gut microbiome.
    Fan L; Zhu X; Sun S; Yu C; Huang X; Ness R; Dugan LL; Shu L; Seidner DL; Murff HJ; Fodor AA; Azcarate-Peril MA; Shrubsole MJ; Dai Q · Clinical nutrition (Edinburgh, Scotland) · 2022
    Randomized trial240 participantsDigestive Health forMagnesium
  9. The Magnesium-Rich Formula for Functional Constipation in Infants: a Randomized Comparator-Controlled Study.
    Benninga MA; MENA Infant Constipation Study Group; Vandenplas Y · Pediatric gastroenterology, hepatology & nutrition · 2022
    Randomized trial286 participantsDigestive Health forMagnesium
  10. Effect of the laxative magnesium oxide on gastrointestinal functional recovery in fast-track colonic resection: a double-blind, placebo-controlled randomized study.
    Andersen J; Christensen H; Pachler JH; Hallin M; Thaysen HV; Kehlet H · Colorectal disease : the official journal of the Association of Coloproctology of Great Britain and Ireland · 2012
    Randomized trial49 participantsDigestive Health forMagnesium
  11. Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies.
    Del Gobbo LC; Imamura F; Wu JH; de Oliveira Otto MC; Chiuve SE; Mozaffarian D · The American journal of clinical nutrition · 2013
    Meta-analysis313,041 participants16 studies pooledCardiovascular Support forMagnesium
  12. Magnesium and the risk of cardiovascular events: a meta-analysis of prospective cohort studies.
    Qu X; Jin F; Hao Y; Li H; Tang T; Wang H; Yan W; Dai K · PloS one · 2013
    Meta-analysis532,979 participants19 studies pooledCardiovascular Support forMagnesium
  13. Quantitative Association Between Serum/Dietary Magnesium and Cardiovascular Disease/Coronary Heart Disease Risk: A Dose-Response Meta-analysis of Prospective Cohort Studies.
    Zhao L; Hu M; Yang L; Xu H; Song W; Qian Y; Zhao M · Journal of cardiovascular pharmacology · 2020
    Meta-analysis544,581 participants18 studies pooledCardiovascular Support Heart Health forMagnesium
  14. Comparative Efficacy of Nutraceuticals on Endothelial Function: A Systematic Review and Network Meta-Analysis.
    Norouzzadeh M; Rashedi MH; Mahdavi-Mazdeh G; Kosari A; Shahinfar H · Current atherosclerosis reports · 2026
    Meta-analysisCardiovascular Support Heart Health forMagnesium
  15. Serum magnesium, mortality, and cardiovascular disease in chronic kidney disease and end-stage renal disease patients: a systematic review and meta-analysis.
    Xiong J; He T; Wang M; Nie L; Zhang Y; Wang Y; Huang Y; Feng B; Zhang J; Zhao J · Journal of nephrology · 2020
    Meta-analysis200,934 participants20 studies pooledCardiovascular Support forMagnesium
  16. Magnesium treatment increases gut microbiome synthesizing vitamin D and inhibiting colorectal cancer: results from a double-blind precision-based randomized placebo-controlled trial.
    Sun E; Zhu X; Ness RM; Murff HJ; Sun S; Yu C; Fan L; Azcarate-Peril MA; Shrubsole MJ; Dai Q · The American journal of clinical nutrition · 2025
    Randomized trial240 participantsDigestive Health forMagnesium
  17. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial.
    Hausenblas HA; Lynch T; Hooper S; Shrestha A; Rosendale D; Gu J · Sleep medicine: X · 2025
    Randomized trial80 participantsEnergy forMagnesium
  18. Total magnesium intake and risk of frailty in older women.
    Struijk EA; Fung TT; Bischoff-Ferrari HA; Willett WC; Lopez-Garcia E · Journal of cachexia, sarcopenia and muscle · 2024
    Cohort study81,524 participantsEnergy forMagnesium
  19. Red blood cell magnesium and chronic fatigue syndrome.
    Cox IM; Campbell MJ; Dowson D · Lancet (London, England) · 1991
    Randomized trial32 participantsEnergy forMagnesium
  20. Exercise, magnesium and immune function.
    Laires MJ; Monteiro C · Magnesium research · 2008
    Narrative reviewEnergy forMagnesium
  21. Perioperative systemic magnesium to minimize postoperative pain: a meta-analysis of randomized controlled trials.
    De Oliveira GS; Castro-Alves LJ; Khan JH; McCarthy RJ · Anesthesiology · 2013
    Meta-analysis1,257 participants20 studies pooledGeneral Health forMagnesium
  22. Long-term outcome after intravenous magnesium sulphate in suspected acute myocardial infarction: the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).
    Woods KL; Fletcher S · Lancet (London, England) · 1994
    Randomized trial2,316 participantsGeneral Health forMagnesium
  23. Association of magnesium sulfate use with mortality in critically ill patients with sepsis: a retrospective propensity score-matched cohort study.
    Gu WJ; Duan XJ; Liu XZ; Cen Y; Tao LY; Lyu J; Yin HY · British journal of anaesthesia · 2023
    Cohort study10,999 participantsGeneral Health forMagnesium
  24. Hypomagnesemia and Mortality in Incident Hemodialysis Patients.
    Li L; Streja E; Rhee CM; Mehrotra R; Soohoo M; Brunelli SM; Kovesdy CP; Kalantar-Zadeh K · American journal of kidney diseases : the official journal of the National Kidney Foundation · 2016
    Cohort study9,359 participantsGeneral Health forMagnesium
  25. The effects of magnesium supplementation on abnormal uterine bleeding, alopecia, quality of life, and acne in women with polycystic ovary syndrome: a randomized clinical trial.
    Jaripur M; Ghasemi-Tehrani H; Askari G; Gholizadeh-Moghaddam M; Clark CCT; Rouhani MH · Reproductive biology and endocrinology : RB&E · 2022
    Randomized trial64 participantsGeneral Health forMagnesium
  26. Effects of magnesium supplementation on improving hyperglycemia, hypercholesterolemia, and hypertension in type 2 diabetes: A pooled analysis of 24 randomized controlled trials.
    Xu L; Li X; Wang X; Xu M · Frontiers in nutrition · 2023
    Meta-analysis1,325 participants24 studies pooledHeart Health forMagnesium
  27. The effect of lowering blood pressure by magnesium supplementation in diabetic hypertensive adults with low serum magnesium levels: a randomized, double-blind, placebo-controlled clinical trial.
    Guerrero-Romero F; Rodríguez-Morán M · Journal of human hypertension · 2009
    Randomized trial82 participantsHeart Health forMagnesium
  28. Positive effects of magnesium supplementation in metabolic syndrome.
    Kisters S; Kisters K; Werner T; Vormann J; Tokmak F; Westhoff T; Gröber U; Predel HG; Reuter H · International journal of clinical pharmacology and therapeutics · 2024
    Randomized trial54 participantsHeart Health forMagnesium
  29. Role of magnesium supplementation in the treatment of depression: A randomized clinical trial.
    Tarleton EK; Littenberg B; MacLean CD; Kennedy AG; Daley C · PloS one · 2017
    Randomized trial126 participantsStress Relief forMagnesium
  30. Effects of Intravenous Esketamine or Magnesium Sulfate on Early Postoperative Negative Emotions and Pain in Patients Undergoing Endoscopic Sinus Surgery: A Randomized Controlled Trial.
    Wang L; Zhou J; Liu Q; Qian K; Wang L; Xie C · Therapeutics and clinical risk management · 2026
    Randomized trial137 participantsStress Relief forMagnesium
  31. Effect of short-term magnesium supplementation on anxiety, depression and sleep quality in patients after open-heart surgery.
    Saba S; Faizi F; Sepandi M; Nehrir B · Magnesium research · 2022
    Non-randomized trial60 participantsStress Relief forMagnesium
  32. Effects of dry needling compared to magnesium infiltration in trigger points for patients with myofascial pain syndrome: a randomized controlled study in Tunisia.
    Dhouibi J; Moncer R; Kalbousi N; Gaddour M; Laayouni S; Ouanes W; Kacem B; Jemni S · Korean journal of family medicine · 2026
    Randomized trial45 participantsStress Relief forMagnesium
  33. Effect of magnesium and vitamin B6 supplementation on mental health and quality of life in stressed healthy adults: Post-hoc analysis of a randomised controlled trial.
    Noah L; Dye L; Bois De Fer B; Mazur A; Pickering G; Pouteau E · Stress and health : journal of the International Society for the Investigation of Stress · 2021
    Randomized trialStress Relief forMagnesium
  34. Magnesium and anabolic hormones in older men.
    Maggio M; Ceda GP; Lauretani F; Cattabiani C; Avantaggiato E; Morganti S; Ablondi F; Bandinelli S; Dominguez LJ; Barbagallo M; Paolisso G; Semba RD; Ferrucci L · International journal of andrology · 2012
    Cohort study399 participantsTestosterone Support forMagnesium
  35. Analysis of the relationship between the blood concentration of several metals, macro- and micronutrients and endocrine disorders associated with male aging.
    Rotter I; Kosik-Bogacka DI; Dołęgowska B; Safranow K; Kuczyńska M; Laszczyńska M · Environmental geochemistry and health · 2017
    Cross-sectional study313 participantsTestosterone Support forMagnesium
  36. Effect of magnesium supplementation in improving hyperandrogenism, hirsutism, and sleep quality in women with polycystic ovary syndrome: A randomized, placebo-controlled clinical trial.
    Gholizadeh-Moghaddam M; Ghasemi-Tehrani H; Askari G; Jaripur M; Clark CCT; Rouhani MH · Health science reports · 2024
    Randomized trial64 participantsTestosterone Support forMagnesium
  37. The effects of trace element supplementation on glycolipid metabolism in PCOS: a systematic review and meta-analysis.
    Yang L; Gao Y; Zhao W; Qi Y; Duo X; Wang H · Frontiers in nutrition · 2025
    Meta-analysis1,600 participants25 studies pooledTestosterone Support forMagnesium
  38. Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion.
    Cinar V; Polat Y; Baltaci AK; Mogulkoc R · Biological trace element research · 2011
    Non-randomized trial20 participantsTestosterone Support forMagnesium