Magnesium level
Serum holds about 0.3% of body magnesium, so a result inside the reference range does not rule out low stores. A common range is 1.82 to 2.31 mg/dL, and research groups propose raising the lower limit to 2.07. Pooled cohorts link lower levels to more cardiovascular disease and diabetes. Magnesium supplements lowered blood pressure about 2 mm Hg in trials.
- Status
- A blood test ordered by a clinician and also sold direct to consumers by some US laboratories. FDA classifies magnesium test systems, used in the diagnosis and treatment of hypomagnesemia and hypermagnesemia, as class I devices [1].
- Measures
- The total concentration of magnesium in serum, a compartment that holds about 0.3% of the body's magnesium [2].
- Also called
- serum magnesium, magnesium serum, magnesium blood test, total serum magnesium, plasma magnesium, Mg, Mg level
- Tested for
- magnesium deficiency, muscle cramps, fatigue, heart rhythm problems, long-term diuretic or acid-reducer use, checking a magnesium supplement
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Linked in research4
- StrongLinked to less cardiovascular disease at higher levels, 30% lower risk per 0.2 mmol/L (0.49 mg/dL) across pooled cohorts, with genetic evidence pointing the same way for coronary disease.
- ModerateLinked to less type 2 diabetes at higher levels, 36% lower risk in the highest category than the lowest across 4 pooled cohorts.
- ModerateShown in trials: magnesium supplements that raised serum magnesium by 0.05 mmol/L lowered blood pressure by about 2 mm Hg over a median 3 months.
- LimitedLimited evidence: one US cohort linked serum magnesium of 1.77 mg/dL or below to about 50% more atrial fibrillation over up to 20 years.
Reported risks0
No risks sourced yet.
Reference ranges
Each range is the one its source published, in mg/dL. Also reported in mmol/L. Where sources differ, each is shown.
Reference interval from the first US National Health and Nutrition Examination Survey, as cited in 2016 and 2021 reviews
| Range | What the source calls it |
|---|---|
| below 1.82 mg/dL | No name given |
| 1.82 to 2.31 mg/dL | "reference range" |
| above 2.31 mg/dL | No name given |
A 2021 review reports that a reference range of 0.75 to 0.95 mmol/L (1.82 to 2.31 mg/dL) can often be found for serum magnesium [3]. A 2016 review traces that interval to a US national survey from 1971 to 1974, where it was the central 95% of results with a mean of 0.85 mmol/L. It was based on the distribution of serum magnesium in a population, not on clinical outcomes [2]. Both reviews argue that the lower limit is too low [2][3].
Magnesium Global Network (MaGNet) recommendation, 2022
People having a serum magnesium test, as a proposed standard lower reference limit · [4], [2], [3], [5]
| Range | What the source calls it |
|---|---|
| below 2.07 mg/dL | "hypomagnesemia" |
| 2.07 or above mg/dL | No name given |
An international group of magnesium researchers recommends standardizing the lower reference value at 0.85 mmol/L (2.07 mg/dL, 1.7 mEq/L). It reports that a US group and a German group reached the same figure independently, because values below it have been associated with a higher risk of several diseases [4][2][3]. An earlier paper by one of the authors proposed the same limit on the ground that reference populations include many people with a chronic latent magnesium deficit [5]. The group states that an evidence-based standard for the upper range has yet to be determined, so this block does not classify high results [4]. The evidence behind the limit is observational. In the group's own collection, 41 of 43 laboratory reference ranges used a lower limit below it [4].
US National Library of Medicine, MedlinePlus Medical Encyclopedia, reviewed 2025
People having the test, as an example of a laboratory normal range · [6]
| Range | What the source calls it |
|---|---|
| below 1.7 mg/dL | "low blood magnesium level" |
| 1.7 to 2.2 mg/dL | "normal range" |
| above 2.2 mg/dL | "high blood magnesium level" |
An encyclopedia entry licensed to the National Library of Medicine, not a guideline. It prints the range as 1.7 to 2.2 mg/dL (0.70 to 0.91 mmol/L) and states that normal value ranges may vary slightly among laboratories [6]. Its lower limit is below both the survey-based 1.82 and the proposed 2.07 [3][4].
What has been shown to move it
Shown to lower it1
Magnesium
Limited evidence: magnesium intake fell below reference values in adults over 12 weeks, and blood magnesium fell slightly in children over a year.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In 35 adults with obesity, magnesium intake stayed below reference values throughout a 12-week ketogenic diet, while serum levels stayed within the reference range [15]. In children on the classic diet, mean plasma magnesium fell from 0.87 to 0.83 mmol/L over 12 months [14].
- Population
- 35 adults with BMI over 30 [15]; 91 children with epilepsy [14].
- Sources
- [14], [15]
- Caveats
- Small studies. Blood levels stayed in range in adults [15].
How it compares with the reference method
Mixed results1
Reference ranges from laboratory to laboratory
Limited evidence: one informal survey found 43 laboratory reference ranges from 16 countries varied widely, and only 2 set the lower limit at 0.85 mmol/L (2.07 mg/dL).
The numbers and sources
- Compared with
- The lower limit of 0.85 mmol/L (2.07 mg/dL) proposed by research groups
- Effect
- Of 43 reference ranges collected from hospitals and laboratory providers, all but 2 had a lower cut-off below 0.85 mmol/L. The authors cite a hospital study in which the share of 20,483 patients classed as low was 7% at a cut-off of 0.65 mmol/L (1.58 mg/dL), 25% at 0.75 mmol/L (1.82 mg/dL) and 60% at 0.85 mmol/L (2.07 mg/dL) [4]. On assay precision, one enzymatic method showed imprecision of 1.7% at 0.72 mmol/L and 1.4% at 1.80 mmol/L, and a mean bias of -1.4% against a reference material [12].
- Population
- 43 reference ranges gathered by researchers from their own institutions and colleagues in 16 countries [4]. Control materials and 101 patient plasma samples in one laboratory [12].
- Sources
- [4], [12]
- Caveats
- The authors describe the collection as informal, so it is not a representative sample of laboratories [4]. The same result can be labeled low by one laboratory and normal by another.
Did not match the reference method1
Serum magnesium as a measure of body stores
Limited evidence: reviews report that serum holds about 0.3% of body magnesium and that a result within the reference range does not rule out deficiency.
The numbers and sources
- Compared with
- The magnesium loading test and total body magnesium
- Effect
- A 2016 review reports that more than 99% of total body magnesium (22 to 26 g in adults) is outside the blood vessels, more than half of it in bone, with only 0.3% in serum. It names the magnesium loading test as the reference measure of magnesium status and reports that serum magnesium does not respond as quickly or consistently as urinary magnesium when deficiency is present [2]. Two further reviews report that magnesium released from body pools, mainly bone, holds the serum level up for a long time, so that a low serum magnesium indicates deficiency while values within the reference range do not exclude it [3][5].
- Population
- Narrative reviews of human studies [2][3][5].
- Sources
- [2], [3], [5]
- Caveats
- These are reviews by authors who also propose raising the lower reference limit, and none pooled diagnostic accuracy data [2][3][5].
What studies tie it to
Linked in research4
Heart and artery disease
Linked to less cardiovascular disease at higher levels, 30% lower risk per 0.2 mmol/L (0.49 mg/dL) across pooled cohorts, with genetic evidence pointing the same way for coronary disease.
The numbers and sources
- Effect
- In a meta-analysis of prospective studies, each 0.2 mmol/L (0.49 mg/dL) higher circulating magnesium was associated with a 30% lower risk of cardiovascular disease (RR 0.70, 95% CI 0.56 to 0.88), with trends toward lower ischemic heart disease (RR 0.83, 95% CI 0.75 to 1.05) and fatal ischemic heart disease (RR 0.61, 95% CI 0.37 to 1.00) [7]. A second meta-analysis found a relative risk of coronary heart disease of 0.86 (95% CI 0.74 to 0.996) comparing the highest with the lowest category, with no significant linear trend [8]. In a Mendelian randomization study, each 0.1 mmol/L higher genetically predicted serum magnesium had an odds ratio for coronary artery disease of 0.88 (95% CI 0.78 to 0.99) [9].
- Population
- 313,041 people in 16 prospective studies, with 11,995 cardiovascular disease events [7]. 38,808 people in 5 cohorts, average follow-up 10.5 years [8]. 60,801 coronary artery disease cases and 123,504 non-cases in a genetic consortium analysis of 48 studies [9].
- Sources
- [7], [8], [9]
- Caveats
- The cohort findings are observational, and the second meta-analysis reports that its results were sensitive to the exclusion of individual studies [8]. The authors of each study call for trials of magnesium to test whether raising the level lowers risk [7][9].
Type 2 diabetes
Linked to less type 2 diabetes at higher levels, 36% lower risk in the highest category than the lowest across 4 pooled cohorts.
The numbers and sources
- Effect
- Comparing the highest with the lowest category of circulating magnesium, the pooled relative risk of type 2 diabetes was 0.64 (95% CI 0.50 to 0.81). The linear association per 0.1 mmol/L (0.24 mg/dL) did not reach significance (RR 0.90, 95% CI 0.81 to 1.002) [8].
- Population
- 31,284 participants in 4 cohorts, 2,680 cases, average follow-up 8.8 years [8].
- Sources
- [8]
- Caveats
- Observational. The authors report that the associations were sensitive to the exclusion of individual studies [8].
Blood pressure, in cohorts and in trials of magnesium supplements
Shown in trials: magnesium supplements that raised serum magnesium by 0.05 mmol/L lowered blood pressure by about 2 mm Hg over a median 3 months.
The numbers and sources
- Effect
- In a meta-analysis of randomized, double-blind, placebo-controlled trials, magnesium at a median 368 mg a day for a median 3 months lowered systolic blood pressure by 2.00 mm Hg (95% CI 0.43 to 3.58) and diastolic by 1.78 mm Hg (95% CI 0.73 to 2.82). Serum magnesium rose by 0.05 mmol/L (95% CI 0.03 to 0.07), about 0.12 mg/dL, compared with placebo [10]. In cohorts, each 0.1 mmol/L higher circulating magnesium was associated with a 4% lower incidence of hypertension (RR 0.96, 95% CI 0.94 to 0.99) [8].
- Population
- 2,028 adults with normal or high blood pressure in 34 trials [10]. 14,876 participants in 3 cohorts, 3,149 cases, average follow-up 6.7 years [8].
- Sources
- [10], [8]
- Caveats
- The trial authors note that residual heterogeneity may remain. The trials ran for months and measured blood pressure, not heart attack or stroke [10].
Atrial fibrillation
Limited evidence: one US cohort linked serum magnesium of 1.77 mg/dL or below to about 50% more atrial fibrillation over up to 20 years.
The numbers and sources
- Effect
- The incidence of atrial fibrillation was 9.4 per 1,000 person-years (95% CI 6.7 to 11.9) in the lowest quartile of serum magnesium (1.77 mg/dL or below) and 6.3 per 1,000 person-years (95% CI 4.1 to 8.4) in the highest (1.99 mg/dL or above). After adjustment, the lowest quartile had a hazard ratio of 1.52 (95% CI 1.00 to 2.31) compared with the upper quartiles. Results were similar after excluding people on diuretics [11].
- Population
- 3,530 Framingham Offspring Study participants free of atrial fibrillation and cardiovascular disease, mean age 44, 228 cases over up to 20 years [11].
- Sources
- [11]
- Caveats
- One observational cohort, and the confidence interval reaches 1.00 [11].
Sources
- US Food and Drug Administration. 21 CFR 862.1495, Magnesium test system. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-862.1495
- Costello RB, Elin RJ, Rosanoff A, et al. Perspective: The Case for an Evidence-Based Reference Interval for Serum Magnesium: The Time Has Come. Advances in Nutrition. 2016. https://doi.org/10.3945/an.116.012765
- Micke O, Vormann J, Kraus A, Kisters K. Serum magnesium: time for a standardized and evidence-based reference range. Magnesium Research. 2021. PMID 34463286. https://pubmed.ncbi.nlm.nih.gov/34463286/
- Rosanoff A, West C, Elin RJ, et al. Recommendation on an updated standardization of serum magnesium reference ranges. European Journal of Nutrition. 2022. https://doi.org/10.1007/s00394-022-02916-w
- Elin RJ. Assessment of magnesium status for diagnosis and therapy. Magnesium Research. 2010. PMID 20736141. https://pubmed.ncbi.nlm.nih.gov/20736141/
- US National Library of Medicine. Magnesium blood test. MedlinePlus Medical Encyclopedia, review date February 13, 2025. https://medlineplus.gov/ency/article/003487.htm
- Del Gobbo LC, Imamura F, Wu JHY, et al. Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies. The American Journal of Clinical Nutrition. 2013. https://doi.org/10.3945/ajcn.112.053132
- Wu J, Xun P, Tang Q, Cai W, He K. Circulating magnesium levels and incidence of coronary heart diseases, hypertension, and type 2 diabetes mellitus: a meta-analysis of prospective cohort studies. Nutrition Journal. 2017. https://doi.org/10.1186/s12937-017-0280-3
- Larsson SC, Burgess S, Michaëlsson K. Serum magnesium levels and risk of coronary artery disease: Mendelian randomisation study. BMC Medicine. 2018. https://doi.org/10.1186/s12916-018-1065-z
- Zhang X, Li Y, Del Gobbo LC, et al. Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials. Hypertension. 2016. https://doi.org/10.1161/HYPERTENSIONAHA.116.07664
- Khan AM, Lubitz SA, Sullivan LM, et al. Low Serum Magnesium and the Development of Atrial Fibrillation in the Community: The Framingham Heart Study. Circulation. 2013. https://doi.org/10.1161/CIRCULATIONAHA.111.082511
- Bailey D, Martens P, Mah W, Yip PM. A next generation enzymatic magnesium assay on the Abbott ARCHITECT chemistry system meets performance goals based on biological variation. Clinical Biochemistry. 2014. https://doi.org/10.1016/j.clinbiochem.2013.09.018