Dietary supplements, as benign as they may seem, when mixed with drugs and other supplements, can lead to unintended consequences.
Certain supplements can aggravate existing medical conditions and impact the potency of prescription drugs and other supplements you might be taking.
And because dietary supplements are not regulated by the Food and Drug Administration the same way food and medicine are, they aren’t approved by the FDA before they hit the market. So, experts say, you may not learn about potential risks until after you’ve already purchased and consumed them. That’s why the FDA recommends always talking to a health care provider before adding a new supplement to your routine.
Magnesium is one of the most popular supplements available, often taken to promote sleep. It can also have benefits for migraines and gut health, but it comes with a risk of interactions with other supplements and medications. Here’s what to know.
What Is Magnesium?
“Magnesium is an essential mineral,” says James Fleet, Ph.D., researcher and professor of nutrition, cellular and molecular sciences at the University of Texas at Austin. “It’s a nutrient that we have to take into our diet to meet specific physiological needs.”
The mineral is essential to producing adenosine triphosphate, or ATP, a cellular energy source. This allows magnesium to contribute to more than 300 chemical processes in the body, according to the Cleveland Clinic. It regulates blood pressure, blood sugar levels, supports muscle function, plays a role in energy production and nerve function, and boosts bone health.
Because magnesium naturally occurs in plant-based foods like nuts, seeds, beans, grains and fruit, most of us get all the magnesium we need from a balanced diet, says Fleet. But people with certain gastrointestinal conditions might have magnesium deficiency requiring a boost from over-the-counter supplements.
The Cleveland Clinic, like the FDA, recommends talking to a health care provider before taking a magnesium supplement.
Too much magnesium can cause diarrhea, nausea, lethargy, impaired kidney function and low blood pressure, among other possible side effects. And the supplement (not food sources of magnesium) carries a risk of interactions with medications and other supplements, adds Fleet, because the dose is isolated and concentrated.
What Is a Drug Interaction?
A drug interaction occurs when a medication works differently from how it would otherwise due to another medication or supplement being taken, a food or beverage that’s been consumed, or a patient’s existing health condition.
For this reason, your health care provider should ask you the medications you’re taking before recommending a new treatment — and your answer should also include supplements.
Certain supplements can interact negatively with drugs, food, beverages, medical conditions and other supplements, Fleet says.
According to the Cleveland Clinic, the risks of such interactions range from more severe side effects to changing how your body absorbs the drug or supplement and reducing their effectiveness.
“A drug interaction is anything that gets in the way of the drug doing its business and, as a result, it makes the job of managing disease harder,” says Fleet.
Health care providers dose medication based on a number of factors, including how it might interact with anything you’re already taking. Pharmacists should alert you if anything you’re taking has a risk of interaction with another part of your health routine — but they have to know the full picture to do so.
Which Drugs and Supplements Interact With Magnesium?
These are the most commonly used medications and supplements that may have an interaction with magnesium supplements, according to Fleet. To be sure you’re not at risk of drug interactions, talk to a health care provider.
AntibioticsTetracyclines, an antibiotic class that treats bacterial infections, are used to treat acne, chlamydia and traveler’s diarrhea, according to the Cleveland Clinic.Fluoroquinolones are a class of antibiotics commonly used to treat complicated bacterial infections that cause urinary tract infections and serious respiratory infections including pneumonia.
Interaction: Magnesium supplements can impact how the body absorbs the antibiotic, which can make the treatment less effective and leave the body still struggling to fight off the infection, says Fleet. The antibiotics can also reduce how much magnesium the body absorbs, but this is less of a concern.
Bone-Loss MedicationBisphosphonates are often prescribed for osteoporosis and other conditions that impact bone density and strength, Fleet says.
Interaction: “This class of drug is very poorly absorbed under the best of circumstances,” says Fleet. In fact, it’s best to take bisphosphonates with water on an empty stomach for the best chance of total absorption. “Having (magnesium) present at the same time could essentially eliminate bisphosphonate absorption,” Fleet adds.
Your doctor might recommend you stop taking magnesium while you’re on the bisphosphonate or separate the times that you take your magnesium and your bisphosphonate by 60 minutes. “Both would allow you to get the full dose of the drug,” says Fleet.
Thyroid MedicationLevothyroxine, a popular medication to treat hypothyroidism and some cancers, is a synthetic version of the thyroid hormone thyroxine, also called T4, per the Cleveland Clinic.
Interaction: Synthetic T4 “can interact directly with magnesium in the gut,” says Fleet, meaning the magnesium can reduce the drug’s effectiveness. “You have to separate them some two to four hours apart from the other drug,” Fleet says.
Calcium SupplementsCalcium is an essential nutrient and mineral that contributes to bone strength, blood clotting and dental health, among many other things. The body doesn’t produce enough of it, according to the Cleveland Clinic, so we have to get it through diet.
Interaction: Calcium doesn’t work well with magnesium, says Fleet, particularly if one dose is much higher than the other because “they are chemically similar.”
While you might find both in bone health supplements, those doses are complementary. But if you take each separately, and your magnesium dose is 2000 milligrams while your calcium dose is a much lower 400 milligrams, the body might have trouble absorbing them, Fleet says.
Both are absorbed in an almost-identical way, adds Fleet, meaning they’ll compete with each other if taken at the same time and reduce each other’s efficacy. Instead of taking them at once, prioritize a separation of a few hours between the two.
How to Avoid a Drug Interaction With Magnesium
If you’re prescribed a drug or take a supplement that interacts with the magnesium supplement you’re taking, your health care provider might suggest a few solutions: stopping the magnesium, stopping the new supplement or medication, changing the dose of either one, or taking them at different times of day from each other, says Fleet.
If you’re concerned about potential drug interactions or are considering adding magnesium to your health routine, talk to a health care provider first.
