7 Side effects when you take magnesium supplements

Many people under magnesium supplementation do not usually experience side effects, but the possibility is never zero.

Some reported major side effects of taking magnesium supplements are relative to high doses [1], such as the following: 

1. Vomiting and nausea  

Magnesium refers to an electrolyte that interacts with the body’s sodium, especially during digestion in the small intestine and colon. 

Severe side effects from magnesium supplements are typically only linked to excessive dosages.

When taken in high amounts, magnesium can cause vomiting and nausea, which is known to be magnesium toxicity or hypermagnesemia. This causes abdominal discomfort or loose stools.

However, vomiting and nausea symptoms are only linked to excessive magnesium consumption. 

It’s rare for people to experience vomiting and nausea due to magnesium supplements, but check with your health professional every time you take new or unfamiliar supplements, and follow the correct dosage.

Also, pregnant women rarely experience magnesium overdose on a normal diet. However, there is a high risk of magnesium overdose for women in general who take magnesium supplements.

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2. Diarrhea and dehydration

Magnesium supplementation promotes the negative stimulation of bowel movements in some pregnant women, which may cause diarrhea, cramping pain, stomach and loss of appetite.

Hence, if a pregnant woman regularly takes magnesium supplements and has experienced diarrhea for two to three days, she needs to seek professional help immediately. 

Untreated diarrhea can lead to dehydration, which is a serious risk during pregnancy as it can affect the amount of amniotic fluid.

diarrhea and dehydration
Photograph: Iakobchuk/Envato

3. Stomach pain

Another common side effect of taking magnesium supplements is abdominal pain along with nausea and vomiting, as mentioned earlier. They may also cause conditions similar to morning sickness. 

Stomach pain usually subsides within several hours of treatment; however, if they still persist, you must notify your health provider right away.

In case a pregnant woman encounters stomach pain after taking magnesium supplements, she needs to go to an emergency room immediately. Magnesium overdose is considered fatal when not treated promptly. 

4. Loss of reflexes 

Excessive intake of magnesium can lead to serious side effects, including the loss of deep tendon reflexes.

Recognizing the signs and having immediate treatment by fluid administration with diuretics can prevent fatal cardiac arrhythmias and lower neuromuscular transmission, leading to respiratory failure [2]. 

5. Cardiac arrhythmias 

Magnesium toxicity can cause irregular heartbeat and cardiac arrest in certain people. Although magnesium supplements are generally well-tolerated, they may also have some adverse effects on cardiovascular health.

Overdose of magnesium supplements can lead to a medical condition known as hypotension, which occurs when your blood pressure drops too low. 

Generally, high blood pressure is damaging, but that does not mean having low blood pressure is good. When you have low blood pressure, you are at a high risk of impaired ability to regulate blood flow, which leads to dizziness or light-headedness. 

Magnesium sulfate has been the focus of some clinical studies in inducing controlled hypotension and lowering patients’ blood pressure for surgery [3]. 

The magnesium doses used were exponentially large, or about 40mg/kg, and were injected by IV; hence, they differ a lot from the set of conditions when taking oral dietary supplements.

In certain circumstances, having long-term supplementation of high magnesium levels in the blood can lead to a slowed heart rate or called bradycardia or irregular heartbeats. 

However, in rare cases, high levels of magnesium are only seen in healthcare settings as a form of therapy or through IV injections.

6. Drowsiness

One major reason people take magnesium supplements is that some forms of the mineral aid in inducing sleep, as magnesium glycinate is present in some supplements.

However, not all of your time is sleeping time. One primary side effect of magnesium is it can cause drowsiness.

Thus, it is better to take magnesium supplements at the end of the day or at night to prevent a midday slump.

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7. Magnesium toxicity

Magnesium toxicity can be diagnosed when the concentration of the mineral in your blood reaches around 1.74 to 2.61 millimoles per liter [4]. When this happens, you may notice some other symptoms, including:

  • Confusion
  • Depression
  • Flushing in the face
  • Low blood pressure
  • Muscle weakness
  • Lethargy
  • Retaining fluid

However, magnesium toxicity is, most of the time, unusual and generally linked to extreme amounts of supplementation or underlying impaired kidney function.

magnesium toxicity
Photograph: nateemee/Envato

Who should avoid magnesium supplements?

Magnesium supplements may be unsafe for people taking diuretics, heart medications or antibiotics [5].

People with diabetes, intestinal disease, heart disease, or kidney disease should only take this supplement if their healthcare provider prescribes it.

For people taking blood sugar-lowering medications, magnesium supplements can increase the body’s absorption of some anti-diabetic medications, like sulfonylurea drugs, which is a good thing. However, the anti-diabetic drug, Metformin, can cause low magnesium levels. 

Those taking blood pressure-lowering medications, magnesium supplements help in reducing blood pressure. It’s important for individuals who take blood pressure medication to consult with their doctor before taking magnesium.

While people with kidney problems, it is important to note that they are at a higher risk of experiencing adverse effects when taking magnesium supplements [6]. 

What medications should you not take with magnesium?

Some medications can interact with magnesium supplements or affect the body’s magnesium levels [7], including the following: 

  • Oral bisphosphonates that are intended for osteoporosis treatment, particularly alendronate (Fosamax). 
  • Diuretic medications, like furosemide (Lasix), may increase magnesium excretion and increase one’s risk of magnesium deficiency. 
  • Proton pump inhibitors, like esomeprazole magnesium (Nexium) which are used to treat acid reflux, can also increase the risk of magnesium deficiency. 
  • Antibiotics, like tetracyclines, fluoroquinolones and nitrofurantoin, can be affected as well by taking magnesium supplements as they can reduce their absorption.
  • Some other antibiotics are quinolone antibiotics, such as levofloxacin (Levaquin) and ciprofloxacin (Cipro), doxycycline (Vibramycin) and demeclocycline (Declomycin)

How do you get rid of magnesium side effects?

You can definitely avoid the major side effects of taking magnesium supplements just by simply following the proper dose. 

The accepted upper limit set by the Food and Nutrition Board (FNB) of the Institute of Medicine (IOM) is 350 mg/day of magnesium supplements. Please keep in mind that this number does not include food sources of magnesium.

Magnesium supplementation paired with a meal or any kind of food can help lower gastrointestinal effects. Hence, do not take these supplements on an empty stomach.

Before taking any supplements, it’s important to conduct research on them. Confirm that there are no known negative effects when taken in conjunction with any medications or drugs you are presently taking.

Plus, you should seek medical advice from a healthcare professional if before taking any supplement.

Lastly, you need to make sure that you are taking a high-quality magnesium supplement adequately formulated with modest levels of magnesium. 

It is always good to stay informed about the things you put in your body. 

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[1] https://pubmed.ncbi.nlm.nih.gov/26404370/ 
[2] https://journal.chestnet.org/article/S0012-3692(20)33132-9/
[3] https://hvmn.com/blogs/blog/supplements-magnesium-side-effects-dosage-and-supplementation#Yosry2008 
[4] https://www.ncbi.nlm.nih.gov/books/NBK554593/ 
[5] https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5637834/ 
[7] https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/ 

The information included in this article is for informational purposes only. The purpose of this webpage is to promote broad consumer understanding and knowledge of various health topics. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen, and never disregard professional medical advice or delay in seeking it because of something you have read on this website.