Can Magnesium Supplements Help Lower Your Blood Pressure?

About half of adults in the United States have high blood pressure. But far fewer actually have their high blood pressure under control. This is partly because over 30 million people should be taking blood pressure medication — but aren’t. 

Taking blood pressure medication is the most effective way to get your high blood pressure within normal range. But there are many ways to lower blood pressure that don’t involve filling a prescription. In addition to changes in diet and physical activity, people are also curious if supplements can help. And one supplement getting a lot of attention lately is magnesium. But does it help?

How are magnesium and blood pressure related?

There are two main ways that magnesium affects blood pressure:

• Magnesium counterbalances the effects of calcium on your blood vessels. Calcium helps blood vessels to constrict. When this happens, your blood pressure goes up. But magnesium binds to the blood vessel wall instead of the calcium. This keeps your blood vessels from tightening, and keeps your blood pressure lower. 

• Magnesium prevents injury to your blood vessel walls. It’s normal for blood vessels to have some wear and tear over time. And this causes the blood vessels to become stiffer, which causes your blood pressure to be higher. Magnesium helps bind up harmful substances that injure your blood vessels, and may help some in the repair process.

But just because magnesium plays a role in blood pressure regulation, does that mean that taking extra magnesium will lower your blood pressure? Let’s take a look.

Does magnesium lower blood pressure?

Studies suggest that magnesium supplements can help lower your blood pressure. But there are a few caveats to be aware of. 

A recent large review study that included almost 3,000 people found that:

• Magnesium supplements helped lower blood pressure, but only by a small amount. 

• On average, systolic blood pressure (the top number) decreased by about 3 points, and diastolic blood pressure (the bottom number) decreased by about 2 points.

• There didn’t appear to be a dose-dependent effect. In other words, more magnesium didn’t lead to larger reductions in blood pressure.

The effect of magnesium on blood pressure was more noticeable in people with either:

• High blood pressure who were already taking blood pressure medication

• Low magnesium levels

Researchers didn’t see any effect in people who had normal blood pressure. This is in line with previous studies showing that magnesium is more likely to lower someone’s blood pressure if they have high blood pressure that’s not controlled.

Another recent review that included over 8,000 people found that:

• Magnesium had an even smaller effect on blood pressure. It only reduced the top and bottom number by about 1 point each.

• The effect was more noticeable at doses over 400 mg per day, and when people took magnesium for over 12 weeks.

What are the side effects of taking magnesium?

It’s important to keep in mind that there can also be some side effects from magnesium supplements. They can include:

• Diarrhea

• Nausea

• Abdominal pain

• Low blood pressure

But most people tolerate magnesium supplements well. In fact, there have been studies looking at magnesium dosages of up to 972 mg per day that didn’t result in significant adverse effects. 

How much magnesium do you need?

In general, the recommended amount of magnesium is:

• 420 mg per day in male adults

• 320 mg per day in female adults

Keep in mind that this is the total daily magnesium amount, including what you get from food and any additional supplements.  

Magnesium supplements for blood pressure

Magnesium supplements come in many forms. And some are absorbed into the blood stream better than others. These are probably better choices if you’re taking magnesium supplements for blood pressure:

• Magnesium citrate

• Magnesium glycinate 

• Magnesium L-threonate

Other common types of magnesium — mainly magnesium oxide — are harder to absorb. This means it tends to stay inside the intestine, which is why it’s more helpful for things like constipation.

But at the end of the day, the type of magnesium is less important than the actual dosage. In studies looking at the effect of magnesium on blood pressure, a typical dosage usually ranged from 300 mg to 400 mg of elemental magnesium per day. Keep in mind that different types of magnesium supplements contain varying amounts of elemental magnesium. 

Is magnesium from food better than supplements?

In general, it’s better to get any nutrient from food than from supplements, when possible. This includes magnesium.

“Your body can usually absorb magnesium more easily when they come from the diet,” said Sarah Samaan, MD, a board-certified cardiologist for over 30 years and GoodRx contributor. “Plus, magnesium-rich foods are full of good nutrition, including fiber and antioxidants.”

Samaan recommends doing a blood test first if you’re considering taking a magnesium supplement. 

“Some conditions, including kidney problems, can affect the way your body handles magnesium,” she said. Magnesium supplements can put you at risk for high magnesium levels in the blood more than magnesium from food.

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Written by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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