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Magnesium injection side effects: A detailed guide

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Magnesium sulfate injection is prescribed for low magnesium blood levels and seizures during pregnancy. It’s an electrolyte replacement that may cause mild or serious side effects. These include sweating and low blood pressure.
Medically reviewed by Alex Brewer, PharmD, MBA
Updated on August 27, 2023

This article describes possible side effects of magnesium sulfate injection. You’ll also find information on cost savings and coupon options for magnesium sulfate. To learn more about magnesium sulfate injection, talk with your doctor or pharmacist.

Magnesium sulfate injection is a generic medication. It isn’t available in a brand-name version.

More common side effects of magnesium

Magnesium sulfate injection may cause mild or serious side effects. Below are some of the more common side effects of this medication.

Commonly reported side effects of magnesium sulfate injection include:

* To learn more about this side effect, see the “Side effects of magnesium in detail” section below.

Mild side effects of magnesium

Magnesium sulfate may cause certain mild side effects. Most often, mild side effects are temporary and can be easily managed. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.

Mild side effects of magnesium sulfate injection that occurred in studies include:

Magnesium sulfate injection may cause more mild side effects than those listed above. For details, see the drug’s prescribing information.

* To learn more about this side effect, see the “Side effects of magnesium in detail” section below.
† An allergic reaction is possible with magnesium sulfate injection. But it wasn’t reported in the drug’s studies.

Serious side effects of magnesium

Magnesium sulfate may cause certain serious side effects. If you have any serious side effects from magnesium sulfate injection, call your doctor right away. But if you think you’re having a medical emergency or your side effects feel life threatening, take immediate action. Call 911 or a local emergency number, or go to the nearest emergency room.

After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Visit MedWatch’s website if you’d like to notify the FDA about a side effect you’ve had with magnesium sulfate.

Serious side effects of magnesium sulfate injection that occurred in studies include:

* This side effect wasn’t reported in studies of magnesium sulfate. But it has occurred after the drug was approved for use in people with seizures during pregnancy.
† To learn more about this side effect, see the “Side effects of magnesium in detail” section below.
‡ An allergic reaction is possible with magnesium sulfate injection. But it wasn’t reported in the drug’s studies. To learn more about this side effect, see the “Side effects of magnesium in detail” section below.

Common questions about side effects of magnesium

Here are answers to some common questions about side effects of magnesium sulfate injection. If you have other questions, talk with your doctor or pharmacist.

Are side effects of magnesium seen in females similar to those seen in males?

Yes, in studies, most side effects of magnesium sulfate were similar in females* and males.*

Females taking magnesium sulfate for seizures during pregnancy may have an additional side effect. Specifically, they may have a low blood calcium level that leads to tetany (unusual muscle cramps or spasms). This side effect wasn’t reported in studies of the drug but has occurred after magnesium sulfate was approved for seizures during pregnancy.

To learn more about your risk of side effects from magnesium sulfate injection, talk with your doctor or pharmacist.

* Sex and gender exist on spectrums. In this article, we use the terms “male” and “female” to refer to a person’s sex assigned at birth.

What are the side effects of too much magnesium?

The side effects of too much magnesium from magnesium sulfate injection are similar to the symptoms of hypermagnesemia. (This is a condition in which blood levels of magnesium are higher than the usual range.)

Side effects may include:

For other possible side effects of too much magnesium, see the “Mild side effects of magnesium” and “Serious side effects of magnesium” sections above.

If you have symptoms of too much magnesium, talk with your doctor. They can check your magnesium level with a blood test. They’ll use the test results to help decide whether to lower your magnesium sulfate dosage or stop treatment.

* To learn more about this side effect, see the “Side effects of magnesium in detail” section below.

Does magnesium cause long-term side effects?

No, long-term side effects aren’t expected with magnesium sulfate injection. In studies, specific side effects weren’t seen in people who received injections for a long time. Long lasting side effects after treatment ended also weren’t reported.

Talk with your doctor if questions about possible long-term side effects of magnesium sulfate injection.

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Side effects of magnesium in detail

Below you’ll find details on some of the side effects of magnesium sulfate injection.

Slow reflexes

Magnesium sulfate injection may cause slow reflexes. This side effect is usually mild. It isn’t known how common slow reflexes were in studies of the drug.

With slow reflexes, your muscles do not respond to a reflex test as quickly as usual.

Ways to manage

If you have concerns about slow reflexes with magnesium sulfate, tell your doctor. They’ll likely check your reflexes often during magnesium sulfate treatment. If you’re found to have slow reflexes, your doctor may lower your magnesium sulfate dosage or stop treatment. 

Flushing

Magnesium sulfate injection may cause flushing. This side effect is usually mild. It isn’t known how common flushing was in studies of the drug.

With flushing, you may have temporary warmth, redness, or deepening of skin color.

Ways to manage

If you have bothersome or long lasting symptoms of flushing, tell your doctor. They can decide whether your symptoms are severe enough to lower your magnesium sulfate dosage or stop treatment.

Low blood pressure

Magnesium sulfate injection may cause low blood pressure. This side effect is usually mild, but it may be serious. It isn’t known how common low blood pressure was in studies of the drug.

With low blood pressure, you may not have any symptoms. But possible symptoms include fatigue (low energy), dizziness, or trouble concentrating. 

Ways to manage

If you have concerns about low blood pressure with magnesium sulfate, tell your doctor. They may check your blood pressure often during magnesium sulfate treatment. If you’re found to have very low blood pressure, your doctor may lower your magnesium sulfate dosage or stop treatment. 

Allergic reaction

For some people, magnesium sulfate injection can cause an allergic reaction. But this side effect wasn’t reported in the drug’s studies.

Symptoms can be mild or serious, and they may include:

  • itchiness
  • skin rash
  • swelling under the skin, usually affecting eyelids, lips, hands, or feet
  • swelling of the mouth, tongue, or throat, which can make it hard to breathe
  • flushing (temporary warmth, redness, or deepening of skin color)

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to magnesium sulfate injection, your doctor may recommend taking a different medication instead.

Warnings for magnesium

Below are some factors you may want to discuss with your doctor before taking magnesium sulfate injection.

Warnings

It may not be safe for you to take magnesium sulfate injection if you have specific health conditions. These are sometimes called drug-condition interactions. Other things may also affect whether magnesium sulfate injection is a safe treatment option for you.

Before receiving magnesium sulfate injection, tell your doctor about your health and medications you take. Things to consider include:

Magnesium and pregnancy

In general, magnesium sulfate injection is considered safe for short-term use during pregnancy. That said, check with your doctor about whether they feel it’s safe for you specifically.

Magnesium and breastfeeding

Magnesium sulfate injection should be taken with caution while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication. Your doctor may recommend other ways to feed your child during treatment with magnesium sulfate.

Magnesium and alcohol

Magnesium sulfate injection is not known to interact with alcohol.

If you drink alcohol, talk with your doctor about whether it’s safe to consume it during your treatment with magnesium sulfate injection.

What to ask your doctor

This article describes common and serious side effects of magnesium sulfate injection. If your doctor prescribes this medication, they can discuss possible side effects with you. Let your doctor know if you have concerns or questions about treatment with this medication.

Here’s a list of some possible questions you may want to ask your doctor:

  • Does my risk of side effects depend on the magnesium sulfate dosage I receive?
  • How do the side effects of magnesium sulfate injection compare with those of oral forms of magnesium?
  • Does my health history raise my risk of side effects from magnesium sulfate injection?

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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