Potassium-depleting diuretics, including thiazide diuretics, cause the body to lose potassium; they may also cause cellular magnesium depletion,3 although this deficiency may not be reflected by a low blood level of magnesium.4 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 thiazide diuretics, should supplement both potassium and magnesium.5
People taking thiazide diuretics should be monitored by their prescribing 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.6 A double-blind trial showed that thiazide diuretic use led to a reduction in blood levels of potassium in some participants. Those experiencing decreased potassium levels were also more likely to experience cardiovascular events, such as heart attacks, stroke, heart failure, aneurysm, and sudden cardiac death.7 Fruit is high in potassium, and increasing fruit intake (especially bananas) is another way of supplementing potassium.
Magnesium supplementation for people taking thiazide diuretics is typically 300–600 mg per day, though higher amounts (over 800 mg per day) have been reported in a controlled study to reduce side effects of thiazides.8 Combining supplementation of both potassium and magnesium has been reported to correct abnormally low blood levels of potassium and also to protect against excessive loss of magnesium.9
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.2 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.
The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
Reduce Side Effects
Potential Negative Interaction
Digitalis (Digitalis purpurea) refers to a family of plants commonly called foxglove, which contains digitalis glycosides, chemicals with actions and toxicities similar to the prescription drug digoxin. Thiazide diuretics can increase the risk of digitalis-induced heart disturbances.1 Thiazide diuretics and digitalis-containing products should be used only 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.2
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.3
Licorice (Glycyrrhiza glabra) may increase the side effects of potassium-depleting diuretics, including thiazide diuretics.4 Thiazide diuretics and licorice should be used together only under careful medical supervision. At the time of this writing, no evidence was found of interactions between deglycyrrhizinated licorice (DGL) and any diuretic was found in the medical literature.
Thiazide diuretics decrease calcium loss in the urine due to actions on the kidneys.1 As a result, it may be less important for some people taking thiazide diuretics to supplement calcium than it is for other people.
Diuretics, including thiazide 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.
The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism.10 However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
1. Threlkeld DS, ed. Diuretics and Cardiovasculars, Thiazides and Related Diuretics. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1993, 135a–7c.
2. Brinker F. Herb Contraindications and Drug Interactions. Sandy, OR: Eclectic Institute, 1997, 102–3.
3. 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.
4. 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.
5. Shaw D et al. Traditional remedies and food supplements: a 5-year toxicological study (1991–1995). Drug Safety 1997;17:342–56.
Please read the disclaimer about the limitations of the information provided here. Do NOT rely solely on the information in this article. The Aisle7 knowledgebase does not contain every possible interaction.
The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2014.
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