Magnesium

Pronunciation: mag-NEE-zee-um.

Generic name
magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others)
Drug class
Essential mineral / electrolyte
Form
Oral tablets/capsules (various salts and strengths); injectable solution (e.g. magnesium sulfate 10-50% w/v)
Route
Oral (tablet, capsule, liquid) for dietary supplementation; oral or intravenous/intramuscular injection for prescription therapeutic use
Legal status
Available over-the-counter as a dietary supplement; prescription-only for specific medical indications (e.g. magnesium sulfate injection)

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: DBL Magnesium Sulfate Concentrated Injection, Phebra, Medsurge, Baxter Ready to Use (7) · Full directory

What magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others) is and how it works

Magnesium is an essential mineral your body needs for normal muscle and nerve function, blood sugar control, blood pressure regulation, and bone structure. It is available as a widely used over-the-counter dietary supplement, and in specific higher-strength prescription forms (such as magnesium sulfate injection) used in hospital or clinician-directed settings for particular medical conditions. (3) (1)

If you are taking an over-the-counter magnesium supplement for general dietary support, follow the product label or your pharmacist's guidance. If magnesium has been prescribed or given to you by a clinician for a specific medical condition (such as during pregnancy for pre-eclampsia/eclampsia, or for significant deficiency), the dose, form, and duration are individually determined by your prescriber or care team -- these are not interchangeable with a standard supplement dose.

Mechanism of action: how magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others) works

Magnesium is a cofactor in more than 300 enzyme systems and acts physiologically as a calcium antagonist at the neuromuscular junction; at pharmacological (injectable) doses it blocks neuromuscular transmission and reduces acetylcholine release, which underlies its anticonvulsant effect in eclampsia/pre-eclampsia. (1) (3)

What magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others) is used for

Dietary supplementation (over-the-counter)

Used to help meet daily magnesium needs or address mild dietary shortfalls, since magnesium is required for hundreds of enzyme reactions in the body, including muscle and nerve function, blood glucose control, blood pressure regulation, and bone health. (3)

Antacid / occasional constipation relief (over-the-counter, certain magnesium salts)

Some magnesium products (such as magnesium oxide or magnesium hydroxide) are also used over-the-counter to relieve acid indigestion or as a short-term laxative, since magnesium salts can have a laxative effect. (2)

Prevention and control of seizures in pre-eclampsia and eclampsia (prescription)

Magnesium sulfate given by injection is used in hospital settings to help prevent seizures in severe pre-eclampsia, and to control seizures in eclampsia, as part of clinician-directed care during pregnancy. (1)

Severe or symptomatic magnesium deficiency (prescription)

Prescription-strength magnesium (oral or injectable, depending on severity) is used under clinician direction to correct significant magnesium deficiency that cannot be managed with diet or standard supplements alone. (3)

Before taking magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others)

Do not take / not appropriate for

  • Do not take magnesium supplements in place of a prescribed prescription-strength magnesium treatment without your clinician's guidance -- the two are not interchangeable. (all countries) (3)

Tell your clinician about

  • Any kidney problems -- reduced kidney function significantly increases the risk of magnesium building up to toxic levels, since the kidneys are the main route of elimination.
  • Pregnancy or breastfeeding.
  • All other medicines you take, especially antibiotics (tetracyclines such as doxycycline, or quinolones such as ciprofloxacin), bisphosphonates for bone health, diuretics ('water tablets'), or proton pump inhibitors, since these can interact with magnesium.
  • Any digestive conditions, since magnesium salts can have a laxative effect.
(3) (2)

How to take magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others)

  • For over-the-counter dietary supplement use, follow the directions on the product label, or your pharmacist's or clinician's advice, since products and strengths vary widely.
  • For prescription-strength or hospital-administered magnesium (such as magnesium sulfate for pre-eclampsia/eclampsia), the dose, route, and duration are set and monitored entirely by your care team -- this is never a self-administered or fixed home dose.
  • If taking oral magnesium alongside certain antibiotics or bisphosphonates, space the doses apart as your pharmacist or prescriber advises, since taking them together can reduce how well those other medicines are absorbed.
(2) (1)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7) (8)

Missed dose

For a missed over-the-counter supplement dose, simply resume your normal schedule at the next dose -- do not double up. Prescription-strength or hospital-administered magnesium is managed entirely by your care team, so a 'missed dose' does not apply in the same way.

Overdose

Seek urgent medical attention if you think too much magnesium has been taken, especially in anyone with kidney problems, or if there are symptoms such as marked weakness, very low blood pressure, or difficulty breathing -- these can be signs of magnesium building up to toxic levels (hypermagnesemia). (1) (3)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Loose stools or a laxative effect, especially with magnesium oxide, hydroxide, or citrate.

What to notice: Loose stools or a laxative effect, especially with magnesium oxide, hydroxide, or citrate.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Mild stomach upset.

What to notice: Mild stomach upset.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

With prescription-strength injectable magnesium: flushing and sweating can occur, particularly at higher doses or infusion rates.

What to notice: With prescription-strength injectable magnesium: flushing and sweating can occur, particularly at higher doses or infusion rates.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of magnesium toxicity (hypermagnesemia), especially with kidney problems or prescription-strength/injectable use — emergency

Symptoms: Flushing, sweating, a marked drop in blood pressure, weak or absent reflexes, severe muscle weakness, or breathing difficulty.

Action: Seek emergency medical attention immediately. This risk is highest in people with reduced kidney function or those receiving prescription-strength/injectable magnesium, which is why clinicians monitor reflexes, breathing rate, and blood magnesium levels closely during treatment, and keep an injectable calcium antidote immediately available. (1) (3)

Reduced kidney function and magnesium buildup — high caution

Symptoms: No specific early symptoms -- the risk is silent until levels rise significantly.

Action: Tell your prescriber about any kidney problems before starting any magnesium supplement or treatment above typical dietary amounts, since reduced kidney function raises the risk of toxic buildup and may require a lower dose or closer monitoring. (3) (1)

Prolonged prescription-strength magnesium use in pregnancy (bone effects in the baby) — high caution

Symptoms: No symptoms noticeable to the mother; risk relates to the baby's bone development with prolonged use.

Action: This risk applies specifically to continuous prescription-strength (e.g. injectable) magnesium given for more than about 5-7 days in pregnancy, which your obstetric care team monitors for and weighs against the benefits of seizure prevention in pre-eclampsia/eclampsia. (1)

Interactions

  • Tetracycline antibiotics (such as doxycycline): magnesium can bind to these antibiotics in the gut and reduce their absorption. Take the antibiotic at least 2 hours before, or 4-6 hours after, a magnesium-containing product. (3)
  • Quinolone antibiotics (such as ciprofloxacin or levofloxacin): the same binding effect reduces antibiotic absorption. Use the same 2-hour-before or 4-6-hour-after spacing. (3)
  • Oral bisphosphonates (used for bone health, such as alendronate): magnesium can reduce their absorption. Take magnesium at least 2 hours before or after the bisphosphonate dose. (3)
  • Certain diuretics ('water tablets') and proton pump inhibitors can affect the body's magnesium levels. (3)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Dietary-level magnesium intake through food and standard supplements is a normal part of pregnancy nutrition; discuss any supplement with your prescriber. Prescription-strength injectable magnesium (magnesium sulfate) is specifically used in pregnancy for pre-eclampsia/eclampsia under close hospital monitoring; continuous use beyond about 5-7 days has been linked to bone effects in the developing baby, so this is carefully weighed by the care team. (1) (2) (3) (4) (5) (6) (7) (8)

Breastfeeding

Magnesium is a normal component of a balanced diet during breastfeeding; discuss any supplement or prescription-strength use with your prescriber. (1) (2) (3) (4) (5) (6) (7) (8)

Children

Dietary magnesium needs apply throughout childhood; prescription-strength/injectable magnesium for specific medical indications in children is directed and dosed entirely by a pediatric specialist. (1) (2) (3) (4) (5) (6) (7) (8)

Elderly

Age-related decline in kidney function can increase the risk of magnesium buildup, so supplement and treatment doses may need closer review in older adults. (1) (2) (3) (4) (5) (6) (7) (8)

Hepatic_impairment

Not a primary route of magnesium elimination; tell your prescriber about any liver conditions regardless. (1) (2) (3) (4) (5) (6) (7) (8)

Renal_impairment

The single most important safety factor for magnesium -- reduced kidney function significantly raises the risk of magnesium toxicity, since the kidneys are the main way excess magnesium is removed from the body. Dose and monitoring are adjusted accordingly by your prescriber. (1) (2) (3) (4) (5) (6) (7) (8)

Monitoring

Before starting

  • Kidney function assessment before any therapeutic (non-dietary) magnesium use
  • Review of other medicines for interactions

During treatment

  • For prescription-strength/injectable magnesium: monitoring of reflexes (such as the knee-jerk reflex), breathing rate, and blood magnesium levels to detect early signs of toxicity.
  • For ongoing supplement use: periodic review with your prescriber if you have kidney problems or take interacting medicines.
(1)

Storage

Store oral supplements at room temperature as directed on the product label, away from moisture. Prescription injectable magnesium sulfate is typically stored at 20-25°C (68-77°F) and protected from freezing; this form is handled by your care team or pharmacy. Keep all forms out of reach of children.

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing/OTC labels and the NIH Office of Dietary Supplements fact sheet; verify against the current full label and local protocol before prescribing or administering.

United States

Indication: Prevention/control of seizures in pre-eclampsia/eclampsia (magnesium sulfate injection)

Dose summary: Individualised per hospital protocol: a loading dose (commonly cited around 4-6 g IV over about 15 minutes, sometimes combined with an IM component) followed by a maintenance infusion (commonly around 1-2 g/hour IV); total daily dose typically not exceeding 30-40 g and reduced in renal impairment. Always protocol- and prescriber-directed, with reflexes, respiratory rate, and serum magnesium monitored throughout.

Renal context: Renal insufficiency significantly increases toxicity risk since magnesium is renally cleared; dose reduction and closer monitoring required. (1)

Mechanism of action

Hepatic guidance

Not a significant route of magnesium metabolism or elimination.

Overdose note

Hypermagnesemia presents with progressive loss of deep tendon reflexes, hypotension, respiratory depression, and in severe cases cardiac conduction abnormalities; managed with IV calcium gluconate as an antagonist, supportive respiratory care, and dialysis in severe renal-impairment cases. (1) (3)

Frequently asked questions

Is magnesium the same whether I buy it over-the-counter or get it as a hospital injection?

No. Over-the-counter magnesium supplements (like magnesium oxide or citrate) are for general dietary support at modest doses. Prescription-strength magnesium, such as magnesium sulfate given by injection, is a different clinical tool used for specific medical situations (like pre-eclampsia/eclampsia) at much higher, closely monitored doses. They are not interchangeable. (2) (1)

Can I take my magnesium supplement at the same time as my antibiotic?

It's best not to. Magnesium can bind to certain antibiotics (tetracyclines and quinolones) in the gut and reduce how much your body absorbs. Space them apart -- generally take the antibiotic at least 2 hours before, or 4-6 hours after, your magnesium. (3)

Who is most at risk of magnesium building up to unsafe levels?

People with reduced kidney function are at the highest risk, since the kidneys are the main way the body clears excess magnesium. This is why kidney function is an important thing to discuss with a prescriber before starting any magnesium supplement above normal dietary amounts, or before receiving prescription-strength magnesium. (3) (1)

What is the mechanism of action of magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others)?

Magnesium is a cofactor in more than 300 enzyme systems and acts physiologically as a calcium antagonist at the neuromuscular junction; at pharmacological (injectable) doses it blocks neuromuscular transmission and reduces acetylcholine release, which underlies its anticonvulsant effect in eclampsia/pre-eclampsia. (1) (3)

What is the generic name of Magnesium?

The generic name is magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others). (3) (2) (1)

What class of drug is magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others)?

Magnesium is classed as: Essential mineral / electrolyte. (3) (2) (1)

References

  1. Magnesium Sulfate Injection, USP -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-29 · source 1
  2. Magnesium Oxide 400 mg Tablet -- OTC Drug Facts labelU.S. Food and Drug Administration / DailyMed (NIH), OTC drug facts label · United States · accessed 2026-07-29 · source 2
  3. Magnesium -- Fact Sheet for Health ProfessionalsNational Institutes of Health, Office of Dietary Supplements (ODS) · United States (general nutrition science reference) · accessed 2026-07-29 · source 3
  4. Magnesium Sulfate 20% w/v Solution for Injection or Infusion -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom · United Kingdom · accessed 2026-07-29 · source 4
  5. Magnesium sulfate -- list of nationally authorised medicinal products (PSUSA)European Medicines Agency (EMA) -- Periodic Safety Update Report Single Assessment (PSUSA) procedure · European Union · accessed 2026-07-29 · source 5
  6. Magnesium Sulfate Injection, USP -- Prescribing Information / Product MonographHealth Canada product monograph · Canada · accessed 2026-07-29 · source 6
  7. Magnesium Sulfate Heptahydrate injection products -- ARTG registrationsTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-29 · source 7
  8. Magnesium Sulphate Injection -- Medsafe approval / Hospital Supply Status (Max Health)Medsafe (New Zealand regulator) · New Zealand · accessed 2026-07-29 · source 8

Brand names by country

Single-ingredient magnesium (various salts: oxide, sulfate, citrate, glycinate, chloride, and others) names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Magnesium Sulfate Injection, USP (multiple manufacturers); Magnesium Oxide (OTC, multiple brands) (1) (2)FDA approved and OTC monograph confirmed · various -- injection 10-50% w/v; OTC tablets commonly 400 mg · multiple manufacturers

United Kingdom

  • Magnesium Sulfate Injection/Infusion (multiple emc-listed products) (4)MHRA licensed emc smpc confirmed · 10%, 20%, 50% w/v · multiple manufacturers

Canada

  • Magnesium Sulfate Injection, USP (6)Health Canada approved confirmed · various · multiple manufacturers

Australia

  • DBL Magnesium Sulfate Concentrated Injection, Phebra, Medsurge, Baxter Ready to Use (7)TGA ARTG registered confirmed · various, e.g. 2.47g/5mL, 2.5g/5mL, 4g/100mL · Pfizer Australia, Phebra Pty Ltd, Medsurge Pharma, Baxter Healthcare

New Zealand

  • Magnesium Sulphate Injection (Max Health) (8)Medsafe approved hospital supply confirmed · not fully enumerated in the source reviewed · Max Health
View brands in additional countries.

European Union

Magnesium sulfate injectable products (nationally authorised across member states) (5)

This page provides general reference information about magnesium and is not a substitute for advice from the clinician or pharmacist managing your care. Dosing and treatment decisions, especially for any prescription-strength or therapeutic (non-dietary) use, should always be made with your prescriber.

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