Does magnesium help with fatigue and low energy?

For most people the trials say no, and the one trial that says yes is small and old. A systematic review of 26 randomized trials in 3,273 people with chronic fatigue syndrome found that most supplements failed, with magnesium one of two exceptions. That exception is a single 1991 trial of magnesium injections in 32 patients, which nobody has repeated. Fatigue is an early sign of real magnesium deficiency, which the NIH calls uncommon in healthy people.

Unsettled. We found no meta-analysis that pools a fatigue effect of magnesium. What exists is one positive injection trial in chronic fatigue syndrome, a later study that found those patients were not short of magnesium, reviews in fibromyalgia and in exercise that found little or no effect, and combination products where magnesium's share cannot be separated. The plausible case is narrow: people who are actually low in magnesium.

What the trials found

Chronic fatigue syndrome

In the 1991 trial, 32 people with chronic fatigue syndrome got a magnesium injection into the muscle every week for 6 weeks, or placebo. Twelve of the 15 on magnesium said they felt better, against 3 of the 17 on placebo (difference 62%, 95% CI 35 to 90). The patients had low red cell magnesium at the start, and it normalized on treatment.

Three years later a study of 89 patients who met the same diagnosis found their red cell magnesium was no different from matched controls, and loading tests in 6 of them showed no deficiency. Its authors concluded there was no indication for magnesium therapy in this condition. Red cell magnesium is an imperfect marker, so neither study settles status. The systematic review of 26 trials says its evidence is too thin for firm conclusions, and its magnesium finding is that one 1991 trial. A BMJ Clinical Evidence review of chronic fatigue syndrome also looked at magnesium by injection, which tells you nothing about tablets.

Fibromyalgia

Fatigue is a core symptom of fibromyalgia. An evidence summary across 7 systematic reviews found that magnesium with malic acid made little or no difference to pain or depressive symptoms. Only one randomized trial sits underneath it, and the abstract does not report fatigue as a pooled outcome. In a 2025 crossover trial of 89 people with fibromyalgia, mostly women around 51, three months of a supplement combining CoQ10, tryptophan and magnesium did not beat placebo on fatigue, the main outcome. Fatigue improved significantly on placebo and the drop on the supplement did not reach significance. Pain, sleep and the overall impact of the illness did improve.

Inflammatory bowel disease

In 98 adults with inflammatory bowel disease in remission, 4 weeks of vitamins B1, B6 and B12 plus magnesium lowered fatigue scores more than placebo (beta -1.98 and -5.19 on the two sections of the fatigue scale, both p below 0.001). Quality of life did not differ. Because four nutrients went in together, the trial cannot say how much, if any, of that came from magnesium.

Energy for exercise

Myth. Magnesium tablets have not been shown to give active people more energy for sport. A review of 12 experimental studies of mixed design, at 116 to 500 mg a day for one day to three months, found most evidence showed no effect on strength, anaerobic or aerobic performance. That review only reaches 1999, and the studies rarely measured magnesium status.

A 2025 trial went the other way. In 15 regular exercisers without deficiency, 300 mg of magnesium chloride twice a day for 9 days lowered aerobic capacity from 44.4 to 41.3 mL/kg/min and 30 second sprint power from 439 to 415 W. The authors called the effect modestly ergolytic, meaning it made performance a little worse, and advised exercisers without low blood magnesium not to supplement.

Recovery is a separate question from energy. A 2024 systematic review found 4 studies in active people where magnesium alone reduced muscle soreness and improved recovery. It pooled no effect size, and soreness is a different outcome from fatigue.

Who should be careful

The NIH sets the upper limit for magnesium from supplements and medicines at 350 mg a day for adults, and 65 to 350 mg for children by age. Magnesium from food does not count toward it. Energy products often stack magnesium with other sources, so every supplement counts toward that limit. High doses from supplements or medicines often cause diarrhea, nausea and abdominal cramps.

Not for everyone. The risk of magnesium toxicity rises when the kidneys work poorly, because they can no longer clear the excess. Tiredness is also a symptom of kidney disease. Anyone with kidney disease who feels tired should raise it with the person treating them rather than reach for magnesium.

Magnesium binds tetracycline and quinolone antibiotics, such as doxycycline and ciprofloxacin. The NIH advises taking those drugs at least 2 hours before or 4 to 6 hours after a magnesium supplement. We have no card on magnesium for fatigue in pregnancy, and none on other medicines.

What expert bodies say

The NIH lists fatigue and weakness among the early signs of magnesium deficiency, alongside loss of appetite, nausea and vomiting. It calls symptomatic deficiency uncommon in healthy people. People with chronic alcoholism, certain health conditions or certain medications are more at risk.

The European Union authorizes the label claim that magnesium contributes to a reduction of tiredness and fatigue. That claim rests on what an essential nutrient does in the body. It was not approved on trials showing that extra magnesium makes well-fed people less tired, and the conditions of use are in the regulation, which we do not quote here. We could not get the NICE guideline on chronic fatigue syndrome, so this page has no NICE position.

How we searched

What would change this answer

• A randomized trial of oral magnesium for fatigue in people with measured low magnesium. The whole plausible benefit lives there, and nobody has tested it directly.
• A repeat of the 1991 trial, ideally with tablets as well as injections. One trial in 32 people is the entire positive case.
• Combination trials with a magnesium alone arm, so the inflammatory bowel disease result could be credited to the right ingredient.
• Access to the NICE guideline, which would give this page an expert position on chronic fatigue syndrome. The trial registry showed no trial of magnesium for fatigue under way.

How much magnesium you need and where it comes from in food is in the magnesium guide. Whether it helps you sleep has its own evidence page.

Sources

1. ev-mgfat-01 · Meta-analysis or systematic review · systematic review of randomized controlled trials · n = 26 RCTs, 3,273 participants
   Most of the supplements failed to show favourable effects for CFS, with the exception of NADH and magnesium.
   
   Who: patients with chronic fatigue syndrome or myalgic encephalomyelitis in randomized trials of complementary therapies
   Effect: magnesium: one placebo-controlled RCT with beneficial effects on symptom profiles; no pooled estimate
   Certainty: Authors: too few RCTs and too small samples for firm conclusions; magnesium evidence is the single 1991 trial.
   BMC Complement Altern Med, 2011 · checked 2026-10-06 · we read the fulltext
2. ev-mgfat-02 · Meta-analysis or systematic review · systematic review with GRADE evaluation · n = —
   CONCLUSIONS: In this systematic review we present information relating to the effectiveness and safety of the following interventions: antidepressants, cognitive behavioural therapy (CBT), corticosteroids, dietary supplements, evening primrose oil, galantamine, graded exercise therapy, homeopathy, immunotherapy, intramuscular magnesium, oral nicotinamide adenine dinucleotide, and prolonged rest.
   
   Who: people with chronic fatigue syndrome
   Effect: intramuscular magnesium listed among interventions assessed; no oral magnesium evidence; no effect estimate in the quoted conclusion
   Certainty: Searches to March 2010; magnesium given by injection, which says nothing about oral supplements.
   BMJ Clin Evid, 2011 · checked 2026-10-06 · we read the abstract
3. ev-mgfat-03 · Meta-analysis or systematic review · Epistemonikos evidence summary with meta-analysis and GRADE · n = 7 systematic reviews, 11 primary studies, 1 randomized trial
   Our conclusion is that the use of magnesium and malic acid in patients with fibromyalgia makes little or no difference on pain and on depressive symptoms.
   
   Who: patients with fibromyalgia (pain, fatigue, insomnia, morning rigidity, depression)
   Effect: little or no difference on pain and depressive symptoms (GRADE summary of findings)
   Certainty: Only one randomized trial underneath; fatigue itself is not reported as a pooled outcome in the abstract.
   Medwave, 2019 · checked 2026-10-06 · we read the abstract
4. ev-mgfat-04 · Randomized controlled trial(s) · systematic critique of experimental studies (Medline 1966-1999) · n = 12 studies
   CONCLUSIONS: Most evidence indicates no effect of Mg supplementation on performance (strength, anaerobic-lactacid, and aerobic).
   
   Who: athletes and active people in experimental magnesium supplementation studies, 116 to 500 mg a day for 1 day to 3 months
   Effect: strength of evidence favors no effect; untrained subjects may benefit more than trained (unconfirmed)
   Certainty: Old (to 1999), mixed designs, no meta-analysis, magnesium status rarely measured; females barely studied. Level B: a narrative critique of experimental studies, not a synthesis of RCTs.
   Clin J Sport Med, 2000 · checked 2026-10-06 · we read the abstract
5. ev-mgfat-05 · Meta-analysis or systematic review · systematic review (PRISMA, PROSPERO CRD42024501822) · n = 4 studies
   RESULTS: These studies showed that MgS reduced muscle soreness, improved performance, recovery and induced a protective effect on muscle damage.
   
   Who: physically active individuals taking magnesium alone (no co-supplements)
   Effect: reduced muscle soreness, improved performance and recovery; no pooled effect size
   Certainty: Only 4 studies, no meta-analysis, soreness rather than fatigue as outcome; full text not in local PMC layer.
   J Transl Med, 2024 · checked 2026-10-06 · we read the abstract
6. ev-mgfat-06 · Randomized controlled trial(s) · randomized, double-blind, placebo-controlled trial · n = 32
   By contrast, 3 of the 17 patients on placebo said that they felt better (difference 62%, 95% CI 35 to 90), and 1 patient had a better energy score.
   
   Who: patients with chronic fatigue syndrome, intramuscular magnesium sulfate weekly for 6 weeks vs placebo
   Effect: 12/15 improved vs 3/17 on placebo (difference 62%, 95% CI 35 to 90); red cell magnesium normalized on treatment
   Certainty: Small, single trial, injected magnesium in people with low red cell magnesium; not replicated (see ev-mgfat-07).
   Lancet, 1991 · checked 2026-10-06 · we read the abstract
7. ev-mgfat-07 · Observational data · case-control study · n = 89
   There is therefore no indication for the use of magnesium therapy in the management of this condition.
   
   Who: 89 patients meeting CFS criteria vs age- and sex-matched controls; 6 had magnesium loading tests
   Effect: no significant difference in red cell magnesium; no deficiency on loading test in 6 patients
   Certainty: Measurement study, not a treatment trial; red cell magnesium is an imperfect marker of status.
   Ann Clin Biochem, 1994 · checked 2026-10-06 · we read the abstract
8. ev-mgfat-08 · Randomized controlled trial(s) · randomized, double-blind, placebo-controlled trial · n = 98
   Compared with placebo, the intervention produced greater reductions in ulcerative colitis (UC) activity measured by P-SCCAI (β = -1.32; p = 0.006) and fatigue assessed by IBD-F Section 1 (β = -1.98; p < 0.001) and Section 2 (β = - 5.19; p < 0.001).
   
   Who: adults with IBD in remission, daily B1, B6, B12 and magnesium vs placebo for 4 weeks
   Effect: IBD-F section 1 beta -1.98 (p < 0.001), section 2 beta -5.19 (p < 0.001); no difference in IBDQ-9 quality of life
   Certainty: Combination product, so the magnesium share of the effect is unknown; short trial.
   Sci Rep, 2026 · checked 2026-10-06 · we read the abstract
9. ev-mgfat-09 · Randomized controlled trial(s) · randomized, double-blind, placebo-controlled crossover trial · n = 89
   Fatigue improved significantly in the placebo group, with a non-significant reduction in the dietary supplement group.
   
   Who: adults with fibromyalgia for at least 2 years (96.6% women, mean age 51), crossover with 3-month periods
   Effect: fatigue improved significantly with placebo, non-significant reduction with the supplement; pain, sleep and impact improved
   Certainty: Combination product; primary fatigue outcome negative, secondary outcomes positive.
   J Diet Suppl, 2025 · checked 2026-10-06 · we read the abstract
10. ev-mgfat-10 · Randomized controlled trial(s) · randomized, double-blind, placebo-controlled crossover trial · n = 15
    Conclusions: In summary, magnesium supplementation had modest ergolytic effects on cycle ergometer exercise performance and mitochondrial respiration.
    
    Who: men and women who were regular exercisers, magnesium chloride 300 mg twice a day for 9 days vs placebo
    Effect: VO2max 44.4 vs 41.3 mL/kg/min (p = 0.005); 30 s sprint power 439 vs 415 W (p = 0.03); 10 km time trial unchanged
    Certainty: Tiny, very short; dose above the 350 mg supplemental UL. Authors advise exercisers without hypomagnesemia not to supplement.
    Nutrients, 2025 · checked 2026-10-06 · we read the abstract
11. ev-mgfat-11 · Position of an expert body · government fact sheet · n = —
    Early signs and symptoms of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness.
    
    Who: people with magnesium deficiency; at risk from chronic alcoholism, certain health conditions or medications
    Effect: fatigue as an early deficiency symptom; symptomatic deficiency uncommon in healthy people
    Certainty: Explains why a benefit is plausible only in people who are actually low in magnesium.
    NIH Office of Dietary Supplements, Magnesium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
12. ev-mgfat-12 · Position of an expert body · EU health claims register entry · n = —
    POL-HC-6401 Magnesium Magnesium contributes to a reduction of tiredness and fatigue Authorised
    
    Who: foods meeting EU conditions of use for magnesium
    Effect: claim status: authorized
    Certainty: Authorized as a general function of an essential nutrient (deficiency logic), not on trials in well-fed people; conditions of use are in Regulation (EU) 432/2012 and not quoted here.
    EU Register on nutrition and health claims, claim POL-HC-6401, snapshot 2026-09-21 · checked 2026-10-06 · we read the section
13. ev-mgfat-13 · Position of an expert body · government fact sheet · n = —
    The Tolerable Upper Intake Level for supplemental magnesium is 350 mg for adults, and it ranges from 65 to 350 mg for children and adolescents, depending on age.
    
    Who: adults; children and adolescents 65 to 350 mg depending on age
    Effect: UL for supplemental magnesium 350 mg/day (adults); food magnesium not counted
    Certainty: Energy products often stack magnesium with other sources; count all supplements toward the UL.
    NIH Office of Dietary Supplements, Magnesium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
14. ev-mgfat-14 · Position of an expert body · government fact sheet · n = —
    The risk of magnesium toxicity increases with impaired renal function or kidney failure because the ability to remove excess magnesium is reduced or lost [1,29].
    
    Who: people with impaired renal function or kidney failure
    Effect: reduced or lost ability to excrete excess magnesium
    Certainty: Fatigue is also a symptom of kidney disease; people with CKD should not self-treat it with magnesium.
    NIH Office of Dietary Supplements, Magnesium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
15. ev-mgfat-15 · Position of an expert body · government fact sheet · n = —
    Although the risk of acquiring too much magnesium from food is low among healthy people, high doses of magnesium from dietary supplements or medications can cause diarrhea, nausea, and abdominal cramping.
    
    Who: people taking magnesium supplements or medications
    Effect: diarrhea, nausea, abdominal cramping at high doses
    Certainty: Food magnesium carries low risk in healthy people.
    NIH Office of Dietary Supplements, Magnesium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
16. ev-mgfat-16 · Position of an expert body · government fact sheet · n = —
    These antibiotics should be taken at least 2 hours before or 4 to 6 hours after a magnesium-containing supplement [57,62].
    
    Who: people taking tetracyclines (doxycycline) or quinolones (ciprofloxacin, levofloxacin)
    Effect: spacing: antibiotic at least 2 h before or 4 to 6 h after magnesium
    Certainty: Interaction from pharmacology references cited by ODS.
    NIH Office of Dietary Supplements, Magnesium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section