Magnesium pills lowered blood pressure about 3 points on top and 2 on the bottom across 38 trials, and they may help most if a blood test shows your magnesium is low.
Magnesium is one of the most popular supplements for blood pressure. Studies show a small average drop, and some people may benefit more than others.
The most useful advice I can give is to ask whether you're low before you buy a bottle. If your level is normal, extra magnesium probably won't do much for your blood pressure.
The book's grade: PLAUSIBLE (mixed evidence). The average effect is small, and it may matter mostly for people who are low. Safety badge: check your meds first. Priority: Optional extras.
How much does magnesium lower blood pressure?
Blood pressure is measured in millimeters of mercury (mmHg), which most people call points.
A 2025 review pooled 38 trials (2025 review of magnesium trials):
- Top number (systolic): down about 3 points.
- Bottom number (diastolic): down about 2 points.
- Doses: about 80 to 640 mg a day, for about 12 weeks.
For example, from 145/90 to about 142/88. A 2026 review of 78 trials found about the same overall drop, 2.5 points on top and 1.6 on the bottom, and called the effects "generally modest" (2026 review of 78 trials).
Who does magnesium help most?
These come from smaller slices of the 2025 review's data, so they're less reliable than the overall result.
- High blood pressure, not on blood pressure pills: no change in the top number; bottom down about 2.
- High blood pressure, on blood pressure pills: top down about 8, bottom down about 3.
- Low magnesium in the blood: top down about 6, bottom down about 5.
- Normal blood pressure: no significant change.
Nobody knows why the drop showed up in people already on pills but not in untreated people. One idea the review authors list is that magnesium may boost the effect of blood pressure medicine.
Why the grade isn't higher
An older Cochrane review of 12 trials in people with high blood pressure found no clear drop in the top number and called the evidence "weak and is probably due to bias" (Cochrane review). The FDA allows a carefully worded label claim about magnesium and blood pressure, but calls the evidence "inconsistent and inconclusive" (NIH magnesium fact sheet).
The 2026 review also said the "clinical significance" of the drop "remains uncertain." The average drop looks real, but it's small, and the studies don't agree enough to call magnesium proven.
Should you get your magnesium checked?
This is the question to bring to your doctor. Some things make running low more likely (NIH magnesium fact sheet):
- Water pills and long-term acid-reducing pills
- Gut diseases
- Type 2 diabetes
- Alcohol dependence
- Older age
If your level is low, your doctor can choose the dose and the form. If it's normal, I'd spend your money and effort elsewhere.
What is the best magnesium dose for high blood pressure?
- Stay at or under 350 mg a day from pills unless your doctor says otherwise. That's the safe upper limit for supplements. The trials' typical dose, about 365 mg, sat just above it.
- More wasn't better. The 2025 review found no link between dose and the size of the drop.
- Time to work: in double-blind trials, about 300 mg a day or about 1 month was enough to raise blood magnesium and lower blood pressure (review of double-blind trials).
- Read "elemental magnesium" on the label. That's the number that counts toward the 350 mg limit.
What is the best form of magnesium for blood pressure?
Studies don't show a clear best form yet. Citrate, chloride, lactate and aspartate absorb better than oxide in small studies. In the 2025 review, the 7 trials that used magnesium chloride showed the biggest drops, but that's too few trials to name a best form.
Food first. Leafy greens, beans, nuts and seeds are good sources. The DASH eating plan is rich in magnesium along with potassium, calcium and fiber, and it lowers blood pressure far more than any magnesium pill.
Is magnesium safe? Who should skip it
- Kidney disease: don't take magnesium unless your doctor tells you to (NIH magnesium fact sheet). That means pills, and also magnesium laxatives and antacids. Weak kidneys can't clear the extra, and the risk of magnesium poisoning goes up. With healthy kidneys, serious poisoning has mostly come from very large doses of laxatives and antacids, more than 5,000 mg a day.
- Diarrhea and cramping are common at high doses, most often with the carbonate, chloride, gluconate and oxide forms.
- Keep it apart from some pills. Take tetracycline-type and quinolone-type antibiotics at least 2 hours before or 4 to 6 hours after magnesium. Keep osteoporosis pills at least 2 hours apart from it. Thyroid pills and some HIV medicines also need to be taken hours apart from magnesium antacids and laxatives. Your pharmacist can give you the timing (thyroid pill label).
- Water pills can push magnesium either way. Many water pills make you lose magnesium in the urine, while spironolactone and similar potassium-keeping pills make you hold on to it. A severe magnesium shortage can also pull your potassium down.
- It can add to your pills. Anything that lowers blood pressure stacks on top of your medicine. If you feel dizzy when you stand, call your doctor the same day.
- Pregnant or breastfeeding? Ask your doctor first.
Which supplements actually lower blood pressure?
The book sorts the main blood pressure supplements this way:
- Potassium is the only supplement that reaches SUPPORTED (works), and the 2025 American Heart Association and American College of Cardiology guideline recommends it "ideally from dietary sources" (2025 AHA/ACC guideline). Store-bought 99 mg potassium pills are NO EVIDENCE (not tested properly), because the trial doses were far bigger. Potassium can be dangerous if you have kidney disease or take certain blood pressure pills, so ask first. My article on salt substitutes covers who must avoid them.
- The reasonable bets, all PLAUSIBLE: hibiscus tea, aged garlic extract, beet juice, magnesium if a blood test shows you're low, and psyllium fiber. Each might take a few points off the top number, and none is a sure thing.
- Coenzyme Q10 and vitamin D are UNLIKELY TO HELP for blood pressure.
No supplement makes up for a poor diet and too little exercise. Diet first, then exercise, then supplements.
How to test magnesium on yourself
With your doctor's blessing, and after a blood test if possible:
- Do a starting home week: two readings in the morning and two in the evening for 7 days. My guide to taking your blood pressure at home covers the steps.
- Change only one thing, at a dose at or under 350 mg a day of elemental magnesium.
- Give it 4 to 8 weeks.
- Do a second home week the same way, and compare the two averages.
- Keep it only if your average came down. A change of less than about 5 points may be noise.
If your numbers are well above your goal, don't let a supplement experiment delay treatment. The book uses 130/80 as its goal so the numbers stay consistent. Your doctor may use 140/90, and that isn't wrong either. If a reading is ever over 180/120, wait a minute and recheck. With symptoms such as chest pain, weakness, a change in vision or trouble speaking, call 911. With no symptoms, contact your doctor's office as soon as possible (the on-call line after hours). If you can't reach a person or get seen that day, go to urgent care.
Bottom line
Magnesium pills lower blood pressure about 3 points on top and 2 on the bottom on average, and the trials disagree on who benefits. They may help most if your blood level is low, so ask about a test before you buy. Stay at or under 350 mg a day from pills, skip them if you have kidney disease, and space them from certain antibiotics, osteoporosis pills and thyroid pills. Use magnesium alongside your medicine, never in place of it.
Questions people ask
Does magnesium lower blood pressure?
A little, on average. Across 38 trials, magnesium lowered the top number about 3 points and the bottom about 2. The drop was bigger in people with low blood magnesium, and there was no significant change in people with normal blood pressure.
How much magnesium should I take for high blood pressure?
Stay at or under 350 mg a day of elemental magnesium from pills unless your doctor says otherwise. About 300 mg a day for about a month was enough to raise blood levels and lower blood pressure in double-blind trials, and higher doses didn't do more.
Is magnesium taurate best for blood pressure?
No form has been shown to be best, taurate included. Citrate, chloride, lactate and aspartate absorb better than oxide in small studies, and the 7 chloride trials showed the biggest drops, which is too few to be sure.
How long does magnesium take to lower blood pressure?
About a month at about 300 mg a day was enough in double-blind trials, though most trials ran about 12 weeks. Give it 4 to 8 weeks, with a home week before and after.
What are the best supplements to reduce blood pressure?
Potassium is the only one graded SUPPORTED, ideally from food. Hibiscus tea, aged garlic extract, beet juice, magnesium if you're low and psyllium are reasonable bets. Each might take a few points off the top number, and none is a sure thing.
The rest of the supplement shelf, graded
Magnesium is one of dozens of supplements graded in my upcoming book, Your Blood Pressure by the Numbers, each with a real number and a safety badge. It also grades products that quietly raise blood pressure, such as real black licorice (HARMFUL), and free changes like isometric handgrip training (SUPPORTED for office readings). It's coming soon.
For another popular option, read what beet juice does for blood pressure, or start with the full ranked list of ways to lower blood pressure.