Medically reviewed by Kristie Reed, PharmD
Magnesium and potassium are two minerals with many different and important effects in your body.
Magnesium plays diverse roles in muscle and nerve signaling, and bone building, and blood glucose and blood pressure control. Potassium is particularly important for muscle contraction, heart rhythms, and fluid balance. Both play a part in blood pressure and blood glucose control.
A majority of Americans don’t get enough of either mineral in their diet. It’s thought that low levels of these minerals may worsen multiple health conditions, such as high blood pressure (hypertension). If you don't get enough magnesium or potassium from diet alone, your healthcare provider may recommend you take a supplement for both. Sometimes the minerals come combined in one dietary supplement.
Besides helping you reach and maintain optimal mineral levels, taking magnesium and potassium may help each other be more effective in certain situations, such as after a kidney transplant.
It’s safe for most people to take magnesium and potassium together. However, you’ll need to be thoughtful about dosage. And it may not be safe for some, especially people with conditions like kidney disease or people who take certain medications.
Benefits of Magnesium
Magnesium plays a role in activating hundreds of chemical reactions in the body. Researchers believe having adequate magnesium levels might benefit multiple medical conditions:
May help prevent or manage diabetes: Many people with type 2 diabetes have low levels of magnesium. Although larger studies are needed on the topic, magnesium supplementation may reduce insulin resistance, which is when your cells don't respond well to the hormone insulin and so glucose (sugar) is not taken out of your blood as well. This is something that can lead to diabetes or be a feature of the disease.
May help with osteoporosis: Having low levels of magnesium may increase the risk of osteoporosis and low bone density. This suggests maintaining proper levels of the mineral can mitigate the risk. However, the role for magnesium supplementation isn’t as clear as other vitamins and minerals, like vitamin D and calcium.
May improve migraine headaches: Migraine headaches have been linked to a low level of magnesium. Some studies have shown that magnesium supplements might reduce the frequency and severity of migraine attacks.
May lower high blood pressure: Research has been conflicting about the role magnesium plays in decreasing blood pressure among people with hypertension. The U.S. Food and Drug Administration (FDA) states that while there may be a benefit, the data are “inconsistent” and “inconclusive.”
Benefits of Potassium
Because potassium plays so many different roles in the body, including triggering chemical reactions and regulating fluids, having low levels may increase your risks of certain illnesses. Maintaining proper levels of potassium might help in the following ways:
May reduce high blood pressure: Low intake of potassium is associated with high blood pressure, and higher intake of potassium may help decrease it.
May prevent a higher risk heart disease and stroke: Lower intake of potassium is associated with increased risk of heart disease and stroke, potentially through its effects on blood pressure. Maintaining proper levels might prevent that increased risk.
May prevent kidney stones: People who have a lower intake of potassium seem to be at higher risk of some types of kidney stones, and some research shows that potassium supplementation may help prevent the stones' formation.
May lower osteoporosis risk: Higher potassium intake seems to be linked to a lower risk of osteoporosis, but the role of potassium supplementation isn’t yet clear.
May prevent a higher risk of type 2 diabetes: Potassium is needed to help secrete insulin, so very low levels of the mineral may promote or worsen diabetes. Because lower potassium intake seems to be linked to increased risk of diabetes, maintaining proper levels might stave off the disease.
Benefits of Taking Magnesium and Potassium Together
Some people may benefit from taking both magnesium and potassium. People who are deficient in one are often deficient in the other. For people who are clearly deficient in both, it’s recommended to replenish them at the same time.
Certain medical conditions and medications may lower levels of both potassium and magnesium and make you need a supplement for each. For example, someone with a disease like ulcerative colitis that interferes with mineral absorption might be deficient in both. Or someone with heart failure might need to take a diuretic to help them urinate more and remove excess fluid. Some diuretics lower both magnesium and potassium.
Because of complex chemical interactions, having low levels of magnesium can further lower your levels of potassium. So correcting a low magnesium level, especially if it’s very low, may help with increasing your potassium as well.
For conditions in which both magnesium and potassium may play a role, like high blood pressure, you might get an enhanced effect from taking both compared to just taking one.
Taking magnesium and potassium together might also help prevent transplant rejection in people who've undergone a kidney transplant. When people are receiving cyclosporine therapy to prevent the rejection, magnesium can reduce the thickening of the kidney's vascular walls that the therapy can cause. Supplementing with potassium can make magnesium even more effective in thinning the walls.
How To Take a Combination of Magnesium and Potassium
Potassium and magnesium are both available as pills or powders. Combination products are also available. Ideally, take both potassium and magnesium with food. In rare medical situations, a healthcare provider might give one or both minerals via an injection.
Potassium is most often sold as a prescription when in the potassium chloride form, but other effective forms are on the market, including potassium citrate, potassium phosphate, potassium gluconate, and potassium bicarbonate. Similarly, magnesium is available in different forms, including magnesium citrate, magnesium oxide, and magnesium chloride.
The ideal dosages of magnesium and potassium—whether taken combined or individually—vary based on your medical conditions, medications, and degree of magnesium or potassium deficiency.
The recommended daily allowance for magnesium, in milligrams (mg), is as follows:
These recommendations are for total intake, including food and any supplements. People who are pregnant or lactating may need slightly higher amounts. Many over-the-counter supplements include around 250-300 mg of magnesium.
There isn’t enough data to set a similar recommended daily allowance for potassium. However, it's been determined that 3,400 mg for men and 2,600 mg for women is probably sufficient for people 19 or older.
The potassium dosage in most over-the-counter supplements is quite a bit lower than that. And there's a history as to why that is.
Research from the 1960s found a risk of small intestine damage in people who were taking a coated version of a potassium supplement. Because of those findings, the FDA requires a label for many products that contain more than 99 mg of potassium.
To avoid having to put the label, most manufacturers only make supplements with 99 mg or less of potassium. For comparison, the following is about how much potassium is in different foods:
So, it’s not clear that using dosages in over-the-counter supplements are going to help boost your potassium much. It’s partly because of this that healthcare providers often recommend increasing potassium through your diet instead of through supplementation.
Related: Foods That Are High in Potassium
Is It Safe To Take Magnesium and Potassium Together?
For most people, it’s likely safe to take low doses of magnesium and potassium together. However, it’s always best to check with a healthcare provider about adding a supplement or mixing supplements, especially in the context of your medical conditions and medications.
Potential Drug Interactions
Some drugs or other supplements affect the absorption of magnesium. Conversely, magnesium may impact the effectiveness of some drugs or increase their risk of side effects. You should check with your healthcare provider about potential interactions, including for some of the following:
Certain antibiotics, such as tetracyclines, aminoglycosides, or quinolones
Osteoporosis medications, such as bisphosphonates like Fosamax (alendronate)
Some drugs for high blood pressure, such as calcium channel blockers like Norvasc (amlodipine)
High doses of vitamin D, calcium, or zinc
For potassium, some drugs may increase the risk of a dangerous condition in which potassium gets too high in your blood, called hyperkalemia. Some examples are:
Angiotensin-converting enzyme (ACE) inhibitors, like Zestril (lisinopril)
Angiotensin II receptor blockers (ARBs), like Cozaar (losartan)
Potassium-sparing diuretics, like Midamor (amiloride)
What To Look For
A healthcare provider will recommend you take a specific dosage of each mineral supplement. You should look for that amount on the product box or bottle.
Because supplements aren’t regulated by the FDA the same way as drugs, consider looking for supplements that have been third-party tested. This means an outside organization has tested the product to ensure the ingredients on the label are actually in the supplement and that those are the only ingredients included. You might see a label from the National Sanitation Foundation (NSF) or the United States Pharmacopeia (USP) on the product to indicate it has gone through such testing.
Can You Take Too Much Magnesium or Potassium?
It’s possible to take too much of one or both of these minerals as supplements.
If taken in extremely high doses—more than 5,000 mg per day—magnesium can cause serious symptoms like muscle weakness, difficulty breathing, low blood pressure, and vomiting. If severe, magnesium toxicity may even lead to a problem with heart rhythm, which can be fatal.
To play it safe, it's recommend that people 9 years or older take no more than 350 mg of magnesium supplements per day. Anything more and you can may experience diarrhea.
Government agencies haven’t set an official limit on the amount of potassium a healthy person can have. That’s because most people's kidneys can safely remove excess potassium through urine.
However, people with certain medical conditions or taking certain medications need to be cautious about their potassium intake. If the potassium blood levels get very high and your kidneys can’t effectively lower it, you can experience hyperkalemia. This can cause shortness of breath and sometimes life-threatening heart rhythm issues.
Because of the risks of hyperkalemia, people with chronic kidney disease may need to limit their intake of potassium—not only in supplements, but also through their diet. Diabetes and diseases of the adrenal glands can also increase the risk of having dangerously high potassium levels.
Side Effects of Taking a Combination of Magnesium and Potassium
There doesn't seem to be research that combining magnesium and potassium causes any side effects on top of any that either supplement on its own might cause.
Magnesium and potassium are both generally well tolerated. Any side effects are usually mild.
The most common side effects of magnesium are diarrhea, gastrointestinal irritation, nausea, and vomiting. The most common side effects of potassium are abdominal pain, burping, diarrhea, gas, nausea, and vomiting.
A Quick Review
Magnesium and potassium are two minerals that play many important roles in the body. A healthcare provider may recommend you take both in supplement form, maybe if you don't get enough of the minerals through your diet alone. Taking the two together likely doesn't pose any additional risk that either supplement has by itself. You should speak with your healthcare provider about the potential risk of magnesium or potassium based on your personal health and medication regimen.
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