Potassium, salt substitutes and blood pressure medicines

What these medicines do to potassium

Medicines such as lisinopril, losartan and spironolactone all reduce how much potassium your kidneys pass out in your urine. That is part of how they work, and on its own it is usually harmless.

Think of it as reducing your kidneys' spare capacity rather than switching it off. Your kidneys can still clear the potassium in an ordinary diet.

The trouble comes from adding a concentrated extra load on top of a reduced capacity — or from stacking two medicines that both act on the same system.

High potassium in the blood is called hyperkalaemia. It is measured with a blood test your prescriber orders, not something you can judge by how you feel.

What the FDA labels say

The lisinopril label is the most explicit. It says using lisinopril with potassium-sparing diuretics such as spironolactone, eplerenone, triamterene or amiloride, with potassium supplements, or with potassium-containing salt substitutes may lead to significant increases in blood potassium, and that if they must be used together it should be with caution and frequent potassium monitoring.

The spironolactone label goes furthest on supplements. Its section is titled 'Drugs and Supplements Increasing Serum Potassium', it warns that combining spironolactone with potassium supplementation may lead to severe hyperkalaemia, and it instructs prescribers that in general potassium supplementation should be discontinued in heart failure patients who start spironolactone. That is an instruction to the prescriber, and it is their decision to make.

The losartan label states the risk more generally: taking losartan with other medicines that raise potassium may cause hyperkalaemia, and potassium should be monitored.

Worth being precise about what is and is not on each label: only the lisinopril label names salt substitutes. The losartan and spironolactone labels do not use that phrase, so anything this guide says about salt substitutes with those two comes from the research below, not from their labels.

All three labels also warn about combining medicines that act on the same hormone system — ACE inhibitors, angiotensin receptor blockers and direct renin inhibitors together — which raises the risk of high potassium, low blood pressure, fainting and kidney problems compared with taking just one.

Where the risk really concentrates

The best evidence is for drug-with-drug combinations. In a network analysis of 27 studies and 43,589 participants with diabetic kidney disease, adding a medicine of the spironolactone family on top of an ACE inhibitor or an angiotensin receptor blocker raised the odds of high potassium roughly six-fold compared with placebo, and about 2.6 to 3.1 times compared with either of those medicines alone.

Real-world data agrees. In a diabetic kidney disease group, high potassium occurred at 22.3 per 100 person-years on the combination versus 10.9 on the single medicine.

It also tends to come back. Between 37 and 49 percent of patients had another raised potassium reading within six months of a first one, with spironolactone use and reduced kidney function among the predictors.

The picture for salt substitutes specifically is more nuanced than the popular warning. In a follow-up analysis of a large stroke-prevention trial with nearly 21,000 participants, of whom 4,828 took one of these blood pressure medicines, a salt made of 75 percent ordinary salt and 25 percent potassium chloride showed no increased rate of high potassium overall, and no difference by whether people were on those medicines.

Read that carefully. It was presented as a conference abstract rather than a full peer-reviewed publication, and the participants largely had reasonably working kidneys. It is a reason not to panic about the topic — it is not clearance to start using one.

Case reports do document severe, life-threatening high potassium from a salt substitute combined with an ACE inhibitor, which resolved when the substitute was removed. The tail risk is real even when the average risk is low.

A review of 32 blood pressure guidelines and 14 kidney guidelines found the advice incomplete and inconsistent, and proposed recommending the 75/25 substitute for hypertensive patients except those with advanced kidney disease, on a potassium supplement, on a potassium-sparing diuretic, or with another reason to avoid it. That exception list is the clearest published answer to 'who does this actually matter for'.

We do not give a figure for how much a gram of potassium chloride raises your blood potassium. No source we relied on measured it.

The mistake most people make

The commonest belief is that a salt substitute is just salt with the bad part taken out — a free swap for blood pressure. What most people never register is that the replacement ingredient is potassium chloride. It is effectively a potassium supplement in a shaker.

The opposite mistake is just as common. Someone hears 'potassium interaction' and starts avoiding bananas, oranges and potatoes, while still using the potassium-based salt substitute every day. That is backwards: it is the concentrated potassium chloride and supplements that deliver a sudden load, and the trial evidence does not support blanket fear of dietary potassium in people with normally working kidneys.

A third mistake is assuming a raised potassium result means the blood pressure medicine has to go. Research shows that reflex stopping is common after a high reading — and these medicines have real heart and kidney benefits. That call belongs to the prescriber, weighing both sides.

Marketing does not help. A product labelled 'salt-free', 'lite' or 'no-salt' is telling you what is missing, not what replaced it. Read the ingredients.

What to do

Keep taking your medicines as prescribed. They protect your heart and kidneys, and any change is a prescriber decision.

Check with your pharmacist or prescriber before starting a salt substitute, a potassium supplement, or a high-potassium electrolyte or sports product.

Ask sooner rather than later if any of these apply to you: you take spironolactone, eplerenone, amiloride or triamterene; you take two blood pressure medicines that act on the same system; or you have been told you have kidney disease, diabetes or heart failure. Those are the groups where the added load matters most.

Spacing your medicine and the potassium apart in the day does not help here. This is about the total load your kidneys have to clear, not about absorption, so timing is the wrong lever.

When to get urgent care

Get urgent medical care for muscle weakness, palpitations, an irregular or slow heartbeat, or numbness and tingling.

High potassium is often completely silent until it affects the heart rhythm, which is why these symptoms are treated as urgent rather than as something to watch.

It is confirmed with a blood test the prescriber orders. There is no way to check it at home.

Sources

• FDA prescribing information, lisinopril (retrieved as the lisinopril/hydrochlorothiazide combination label) — Agents Increasing Serum Potassium: "Use of lisinopril with potassium-sparing diuretics (e.g., spironolactone, eplerenone, triamterene, or amiloride), potassium supplements, or potassium-containing salt substitutes may lead to significant increases in serum potassium." (effective 2026-06-02) (FDA label 00b266d9-ac4a-e931-e063-6294a90a6a0b, retrieved 2026-08-15)
• FDA prescribing information, spironolactone — §7.1 Drugs and Supplements Increasing Serum Potassium: "Concomitant administration of spironolactone with potassium supplementation or drugs that can increase potassium may lead to severe hyperkalemia. In general, discontinue potassium supplementation in heart failure patients who start spironolactone." Salt substitutes are NOT named on this label. (effective 2025-11-19) (FDA label 08738ad4-1607-4d55-af71-6790477353bd, retrieved 2026-08-15)
• FDA prescribing information, losartan potassium — §7.1 Agents Increasing Serum Potassium: "Coadministration of losartan with other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients." Salt substitutes and potassium supplements are NOT named on this label. (effective 2025-10-22) (FDA label 021cd76a-b093-4704-8410-5e7d01e20a54, retrieved 2026-08-15)
• Luo, X., et al. (2023). Influence of SGLT2i and RAASi and their combination on risk of hyperkalemia in DKD: a network meta-analysis. Clinical Journal of the American Society of Nephrology, 18(8), 1019–1030.
• An, J., Niu, F., & Sim, J. J. (2021). Cardiovascular and kidney outcomes of spironolactone or eplerenone in combination with ACEI/ARBs in patients with diabetic kidney disease. Pharmacotherapy, 41(12), 998–1008.
• Adelborg, K., et al. (2019). Predictors for repeated hyperkalemia and potassium trajectories in high-risk patients — a population-based cohort study. PLoS ONE, 14(6), e0218739.
• Yin, X., et al. (2025). Risks of hyperkalaemia with potassium-enriched salt substitute among patients using concomitant RAAS blockade in the Salt Substitute and Stroke Study. Hypertension (abstract FR559). — conference abstract, not a full peer-reviewed paper.
• Ray, K. K., et al. (1999). Severe hyperkalaemia due to the concomitant use of salt substitutes and ACE inhibitors in hypertension: a potentially life threatening interaction. Journal of Human Hypertension.
• Xu, X., et al. (2024). Potassium-enriched salt substitutes: a review of recommendations in clinical management guidelines. Hypertension.
• Romero-González, G., et al. (2022). The "fifty shadows" of the RALES trial: lessons about the potential risk of dietary potassium supplementation in patients with chronic kidney disease. Journal of Clinical Medicine.

Reviewed for general accuracy against peer-reviewed literature. Last updated August 2026.