Potassium-depleting diuretics, including loop diuretics, cause the body to lose potassium. Loop diuretics may also cause cellular magnesium depletion,1 although this deficiency may not be reflected by a low blood level of magnesium.2 Magnesium loss induced by potassium-depleting diuretics can cause additional potassium loss. Until more is known, it has been suggested that people taking potassium-depleting diuretics, including loop diuretics, should supplement both potassium and magnesium.3
People taking loop diuretics should be monitored by their doctor, who will prescribe potassium supplements if needed. Such supplementation is particularly critical before surgery in patients with a history of heart disease. In a preliminary study, people with low blood levels of potassium (in part related to diuretic use) had a higher incidence of serious problems resulting from surgery (including death) compared with those having normal potassium levels.4 Fruit is high in potassium, and increasing fruit intake is another way of supplementing potassium. Magnesium supplementation is typically 300–400 mg per day.
One study showed that people taking diuretics for more than six months had dramatically lower blood levels of folic acid and higher levels of homocysteine compared with individuals not taking diuretics.5 Homocysteine, a toxic amino acid byproduct, has been associated with atherosclerosis. Until further information is available, people taking diuretics for longer than six months should probably supplement with folic acid.
People with congestive heart failure (CHF) treated with the loop diuretic furosemide may be at risk for vitamin B1 deficiency due to: 1) the disease, 2) treatment with furosemide, and/or 3) inadequate dietary vitamin B1 intake.6 In a study of people with CHF, long-term furosemide therapy was associated with clinically significant vitamin B1 deficiency due to urinary losses.7 This furosemide-induced vitamin B1 deficiency may worsen heart function in patients with CHF and may be prevented or corrected with vitamin B1 supplementation.8
Digitalis (Digitalis purpurea) refers to a family of plants commonly called foxglove that contain digitalis glycosides, chemicals with actions and toxicities similar to the prescription drug digoxin. Loop diuretics can increase the risk of digitalis-induced heart disturbances.9 Loop diuretics and digitalis-containing products should only be used under the direct supervision of a doctor trained in their use.
Herbs that have a diuretic effect should be avoided when taking diuretic medications, as they may enhance the effect of these drugs and lead to possible cardiovascular side effects. These herbs include dandelion, uva ursi, juniper, buchu, cleavers, horsetail, and gravel root.10
Use buckthorn (Rhamnus catartica, Rhamnus frangula, Frangula alnus) or alder buckthorn for more than ten days consecutively may cause a loss of electrolytes (especially the mineral potassium). Medications that also cause potassium loss, such as some diuretics, should be used with caution when taking buckthorn or alder buckthorn.11
Licorice (Glycyrrhiza glabra) may enhance the side effects of potassium-depleting diuretics, including loop diuretics.12 Loop diuretics and licorice should be used together only under careful medical supervision. Deglycyrrhizinated licorice (DGL) may be used safely with all diuretics.
Diuretics, including loop diuretics, cause increased loss of sodium in the urine. By removing sodium from the body, diuretics also cause water to leave the body. This reduction of body water is the purpose of taking diuretics. Therefore, there is usually no reason to replace lost sodium, although strict limitation of salt intake in combination with the actions of diuretics can sometimes cause excessive sodium depletion. On the other hand, people who restrict sodium intake and in the process reduce blood pressure may need to have their dose of diuretics lowered.
1. Martin B, Milligan K. Diuretic-associated hypomagnesiumia in the elderly. Arch Intern Med 1987;147:1768–71.
2. Kroenke K, Wood DR, Hanley JF. The value of serum magnesium determination in hypertensive patients receiving diuretics. Arch Intern Med 1987;147:1553–6.
3. Whang R, Whang DD, Ryan MP. Refractory potassium repletion—a consequence of magnesium deficiency. Arch Intern Med 1992;152:40–5.
4. Wahr JA, Parks R, Boisvert D, et al. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. JAMA 1999;281:2203–10.
5. Morrow LE, Grimsley EW. Long-term diuretic therapy in hypertensive patients: effects on serum homocysteine, vitamin B6, vitamin B12, and red blood cell folate concentrations. South Med J 1999;92:866–70.
6. Brady JA, Rock CL, Horneffer MR. Thiamin status, diuretic medications, and the management of congestive heart failure. J Am Dietet Assoc 1995;95:541–4.
7. Seligman H, Halkin H, Rauchfleisch S, et al. Thiamine deficiency in patients with congestive heart failure receiving long-term furosemide therapy: A pilot study. Am J Med 1991;91:151–5.
8. Shimon I, Almog S, Vered Z, et al. Improved left ventricular function after thiamine supplementation in patients with congestive heart failure receiving long-term furosemide therapy. Am J Med 1995;98:485–90.
9. Threlkeld DS, ed. Diuretics and Cardiovasculars, Thiazides and Related Diuretics. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons Drug Information, Apr 1993, 135a–7c.
10. Brinker F. Herb Contraindications and Drug Interactions. Sandy, OR: Eclectic Institute, 1997, 102–3.
11. European Scientific Cooperative on Phytotherapy (ESCOP). Frangulae cortex, frangula bark. Monographs on the Medicinal Uses of Plant Drugs. Exeter, UK: University of Exeter, Centre for Complementary Health Studies, 1997.
12. Shintani S, Murase H, Tsukagoshi H, Shiigai T. Glycyrrhizin (licorice)-induced hypokalemic myopathy. Report of two cases and review of the literature. Eur Neurol 1992;32:44–51.
Last Review: 05-01-2013
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