Can You Take Magnesium While on Diuretics?
Summary
Often, yes, but it depends on the type of diuretic you take and your kidney function. Some diuretics can increase magnesium loss, while magnesium supplements can interact with medications and may be unsafe in people at risk for high magnesium levels.
The Short Answer
Many people taking loop or thiazide type diuretics can take magnesium, but it is not a universal green light.
Loop and thiazide like diuretics can increase magnesium loss in urine, and low magnesium has been reported in diuretic users, including links with heart rhythm problems in some cases. This is described in research on diuretic therapy and magnesium status (PubMed: “Relationship of diuretic therapy and serum magnesium levels ...”) and in a review of magnesium interactions with cardiovascular drugs (PubMed: “Magnesium and cardiovascular drugs: interactions and therapeutic ...”).
At the same time, magnesium supplements can interact with certain medications or affect magnesium status, so it is worth checking your full medication list with a clinician or pharmacist. The NIH Office of Dietary Supplements notes that several types of medications can interact with magnesium supplements or affect magnesium status (NIH ODS: “Magnesium, Health Professional Fact Sheet”).
Important: Do not start magnesium on your own if you have kidney disease, a history of high magnesium, or you are on multiple heart or blood pressure medicines. Reduced kidney clearance can allow magnesium to build up, and the safest plan is individualized dosing and lab monitoring.
Why diuretics change magnesium levels
Not all “water pills” behave the same way.
Thiazide and thiazide like diuretics can increase urinary magnesium excretion, and prolonged use can contribute to total body magnesium deficiency. This increased magnesiuresis is highlighted in PubMed reviews on diuretic therapy and magnesium levels and on magnesium interactions with cardiovascular drugs (PubMed: “Relationship of diuretic therapy and serum magnesium levels ...”, PubMed: “Magnesium and cardiovascular drugs: interactions and therapeutic ...”).
Low magnesium is not just a lab value. The same PubMed review notes that low magnesium has been associated with cardiac arrhythmias in diuretic users (PubMed: “Relationship of diuretic therapy and serum magnesium levels ...”). If you already have heart disease (including conditions such as Valvular Heart Disease), your clinician may be more proactive about checking electrolytes.
Potassium sparing diuretics are different. Some reduce potassium loss, and depending on the exact drug and your kidney function, electrolyte patterns can shift in ways that change what “safe” looks like.
When magnesium is more likely to be helpful vs risky
Magnesium is most commonly considered when there is a reason to suspect low levels, such as symptoms plus a medication that increases losses.
Situations where a clinician may be more likely to consider magnesium include:
Risk tends to rise when magnesium can accumulate or when medication interactions are likely.
What the guidelines say about doses (and a practical approach)
Dietary magnesium from food is generally considered safe for most people, but supplements are where side effects and excess intake are more likely.
According to the NIH Office of Dietary Supplements, the tolerable upper intake level (UL) for supplemental magnesium for adults is 350 mg per day, largely based on the risk of diarrhea and gastrointestinal upset. This UL does not apply to magnesium naturally present in foods (NIH ODS: “Magnesium, Health Professional Fact Sheet”).
A practical, clinician friendly way to think about it:
Pro Tip: If diarrhea happens, it is often dose related. Ask your clinician whether splitting the dose or switching the form of magnesium could help, and do not “push through” severe GI symptoms since dehydration can worsen electrolyte issues when you are on a diuretic.
Warning signs: when to pause magnesium and get medical advice
Some symptoms should prompt a quick check in, especially if you recently changed a diuretic dose, started a new supplement, or had vomiting or diarrhea.
Contact a clinician promptly if you notice:
If symptoms are severe or sudden, seek urgent care.
Key takeaways for people on diuretics
Sources & References
- Relationship of diuretic therapy and serum magnesium levels ... - National Institutes of Health
- Magnesium and cardiovascular drugs: interactions and therapeutic ... - National Institutes of Health
- Magnesium - Health Professional Fact Sheet - National Institutes of Health
- Effects of Magnesium Supplementation on Blood Pressure - Ahajournals
Frequently Asked Questions
- Do potassium sparing diuretics change whether magnesium is safe?
- They can. Potassium sparing diuretics have different electrolyte effects than loop or thiazide diuretics, so the risk of imbalance depends on the specific drug and your kidney function. Because magnesium supplements can interact with medications, it is best to confirm safety with your prescriber or pharmacist (NIH ODS: “Magnesium, Health Professional Fact Sheet”).
- Is magnesium from food safer than a supplement if I take a diuretic?
- For most people, yes. The NIH Office of Dietary Supplements notes that the upper limit of 350 mg per day applies to supplemental magnesium, not magnesium naturally found in foods (NIH ODS: “Magnesium, Health Professional Fact Sheet”). If you have kidney disease, discuss even high dietary intake with your clinician.
- Can magnesium make my blood pressure drop too low with a diuretic?
- Possibly for some people. Research in an American Heart Association journal suggests magnesium supplementation may slightly lower blood pressure (AHA Journals: “Effects of Magnesium Supplementation on Blood Pressure”), which could add to a diuretic’s effect. If you feel lightheaded, especially when standing, ask your clinician whether you should adjust timing or dose.
- Should I get my magnesium level tested if I am on a thiazide or loop diuretic?
- It is reasonable to ask. Studies report increased magnesium loss and low serum magnesium among users of thiazide like and loop diuretics (PubMed: “Relationship of diuretic therapy and serum magnesium levels ...”, PubMed: “Magnesium and cardiovascular drugs: interactions and therapeutic ...”). Your clinician can decide whether testing is needed based on symptoms, dose, duration, and kidney function.
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