Quick answer

Ask your pharmacist or doctor before combining. NIH names 3 kinds of diuretic that change magnesium loss in 2 directions: loop and thiazide types can increase the magnesium lost in urine, and potassium-sparing types reduce it. The furosemide label says the medicine may lower blood magnesium, so levels should be checked periodically.^1,2,3

Key facts

The furosemide label says the medicine may lower blood levels of calcium and magnesium, and that both should be checked periodically.³
The hydrochlorothiazide label lists low magnesium among the fluid and electrolyte disturbances to watch for, and says low potassium and low magnesium can provoke heart rhythm problems.⁴
NIH's upper limit for magnesium from supplements and medicines is 350 mg a day for adults, and it does not count magnesium in food and drinks.²
Magnesium is also found in some laxatives and in some products for heartburn and indigestion.²

Ask your pharmacist or doctor first

Long-term use of loop diuretics such as furosemide, and of thiazide diuretics such as hydrochlorothiazide, can increase the magnesium lost in urine, while potassium-sparing diuretics such as spironolactone reduce it. The furosemide label says it may lower blood magnesium and that levels should be checked periodically.^1,2,3

On the medicine's label

Do diuretics lower magnesium?

Some do. NIH's health professional sheet says chronic treatment with loop diuretics such as furosemide and bumetanide, and with thiazide diuretics such as hydrochlorothiazide, can increase the magnesium lost in urine and lead to magnesium depletion. Its consumer sheet makes the same point in one line: diuretics can either increase or decrease the loss, depending on the type.^1,2

The labels describe it from the medicine's side. The furosemide label says the medicine may lower serum magnesium and calcium and advises periodic checks of both. The hydrochlorothiazide label counts low magnesium among the disturbances to watch for, and warns that low potassium and low magnesium can provoke heart rhythm problems.^3,4

What about potassium-sparing diuretics such as spironolactone?

NIH says potassium-sparing diuretics such as amiloride and spironolactone reduce magnesium excretion. The spironolactone label reads differently: besides high potassium, it says the medicine can cause low sodium, low magnesium and low calcium, and that electrolytes should be monitored periodically. The two sources do not match on magnesium, which is one more reason the answer for you comes from your own blood tests.^1,5

Does the form matter: glycinate, citrate or oxide?

The NIH sheets and the diuretic labels speak about magnesium itself and name no form. The sources checked do not say that glycinate, citrate or oxide behaves differently with a diuretic. That is not a finding either way, so give your pharmacist the exact name printed on your product.^1,2

Two of those forms also come as everyday medicines. Magnesium citrate is sold as a saline laxative and magnesium oxide as an antacid. The antacid label says to ask a doctor before use if you have kidney disease or take a prescription drug, and the laxative label asks you to check with a doctor or pharmacist if you take any other drug.^6,7

NIH counts magnesium from supplements and medicines toward its 350 mg a day upper limit for adults, so a laxative or antacid taken for another reason adds to the total.²

Questions to take to the pharmacy

Is my diuretic a loop, thiazide or potassium-sparing type?
Has my blood magnesium been checked since I started it, and when is the next test?
Which form of magnesium is in my product, and do any of my other products, such as an antacid or a laxative, contain it too?
Does my kidney function change the advice?

Questions people ask

Can you take magnesium glycinate with diuretics?

NIH and the labels speak about magnesium without naming a form, so glycinate does not remove the need to ask. Your pharmacist can check your diuretic against the product.^1,3

What happens with magnesium and thiazide diuretics?

NIH says thiazide diuretics such as hydrochlorothiazide can increase the magnesium lost in urine. The hydrochlorothiazide label lists low magnesium among the disturbances to watch for.^1,4

What about magnesium and loop diuretics?

NIH says chronic treatment with loop diuretics such as furosemide can lead to magnesium depletion, and the furosemide label says the medicine may lower blood magnesium. Ask whether your levels have been checked.^1,3

Is magnesium citrate or magnesium oxide different with diuretics?

The sources checked do not separate forms. Citrate and oxide are also sold as a laxative and an antacid, and those labels tell people to ask a doctor before use if they take other drugs or have kidney disease.^6,7

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.