Nutrients and interactions
Supplements if you take a diuretic
Thiazide and loop diuretics make you lose potassium, thiazides are also linked to low magnesium, and loop diuretics increase thiamine loss; potassium-sparing diuretics such as spironolactone do the opposite and retain potassium. That split decides everything here, because a potassium supplement that helps on a thiazide can cause life-threatening high potassium on spironolactone. Picks are ranked by the evidence that the drug lowers the nutrient. This page is about nutrients and interactions: never stop or change a diuretic, or add potassium, without your prescriber and a blood test.
This page covers nutrients and supplement interactions. Never stop or change a prescribed medication without your prescriber, and check any new supplement with your pharmacist.
Evidence last reviewed: October 2026
Top picks
| Option | Evidence | Best for | The honest note | |
|---|---|---|---|---|
| Potassium | Strong evidence | thiazide or loop users, after testing | Thiazide users had 11 times the risk of low potassium in a 10-year population cohort, and loop diuretics are linked to it too. Replace only after a blood test; over-the-counter pills are capped at 99 mg, and potassium with a potassium-sparing diuretic is a recognized cause of life-threatening hyperkalemia. | View |
Solid options
| Option | Evidence | Best for | The honest note | |
|---|---|---|---|---|
| Magnesium | Moderate evidence | thiazide users with low levels | In a study of 5,179 older adults, thiazide use was independently associated with low magnesium. Test first; 200–400 mg of elemental magnesium is the usual range, but avoid it on spironolactone or amiloride, or with reduced kidney function, unless your doctor advises it. | View |
Situational
| Option | Evidence | Best for | The honest note | |
|---|---|---|---|---|
| Vitamin B1 (Thiamine) | Moderate evidence | long-term loop diuretics in heart failure | Thiamine deficiency is more common in heart failure (odds ratio 2.53), and loop diuretics increase urinary thiamine loss. A maintenance dose of 50–100 mg a day is reasonable to discuss with your doctor; it is very safe but not a heart failure treatment. | View |
Skip, or avoid with this medication
- Licorice Root Moderate evidence
Glycyrrhizin lowers potassium on its own, and together with thiazide or loop diuretics it has caused severe hypokalemia.
- Senna Moderate evidence
Stimulant laxatives add potassium and magnesium loss to the diuretic's, so keep them to short courses and have electrolytes checked if used longer.
- Herbal Diuretic Formulas Limited evidence
The one controlled test of dandelion found no diuretic effect, and stacking these herbs on a prescription diuretic risks dehydration and low potassium.
- Electrolyte Powder Moderate evidence
Useful after heavy sweating, but high-potassium formulas are risky with spironolactone, and high-sodium servings work against blood pressure treatment.
- Calcium Moderate evidence
Thiazides reduce calcium excretion, so calcium supplements on top can push blood calcium too high; have calcium checked rather than supplementing blind.
- Leg Cramp Formulas Limited evidence
A Cochrane review found magnesium unlikely to meaningfully reduce idiopathic cramps in older adults, and potassium-containing blends are risky with potassium-sparing diuretics.
Our verdict
On a thiazide or loop diuretic, ask for potassium and magnesium levels and let your prescriber decide on replacement, which is usually food or a prescription rather than a 99 mg pill. On spironolactone, eplerenone, amiloride or triamterene, avoid potassium supplements, salt substitutes and high-potassium formulas. Skip licorice, stimulant laxatives and herbal water pills, which deepen potassium loss.