Hydrochlorothiazide (HCTZ) is a widely prescribed medication for high blood pressure and fluid retention. As a thiazide diuretic, it helps the kidneys remove excess salt and water, lowering blood pressure and reducing swelling.
However, it also impacts potassium levels, which our body needs for nerve signaling, muscle contractions, and fluid balance. Research on US adults between 1999 and 2018 found that around 2 million people taking HCTZ had low potassium levels.
This article explains the connection between HCTZ and potassium levels, including the risks involved and what you can do to maintain healthy levels while taking it.
| 🔑 Key Takeaways ➤ A drop in potassium levels can cause mild to severe symptoms, including muscle weakness, fatigue, abnormal heart rhythms, and in extreme cases, life-threatening complications. ➤ The higher the HCTZ dose, the greater the risk of potassium loss. ➤ A diet high in sodium can worsen potassium loss, while increasing potassium-rich foods like bananas, potatoes, and spinach can help counteract the effects of HCTZ. ➤ Certain drugs, including corticosteroids, beta-2 agonists, antifungal medications, and loop diuretics, can increase potassium depletion when combined with HCTZ. ➤ Conditions such as chronic kidney disease, heart failure, and hyperaldosteronism can make individuals more susceptible to potassium imbalances. ➤ If potassium loss remains an issue, switching to a potassium-sparing diuretic or an alternative blood pressure medication, such as ACE inhibitors or beta-blockers, may be necessary. |
The Connection Between Hydrochlorothiazide and Potassium Levels
When excess fluid builds up in the bloodstream, often due to high sodium (salt) levels or fluid (water) retention, it forces your heart to work harder to pump the increased volume through blood vessels. Over time, this added strain raises blood pressure.
Hydrochlorothiazide (HCTZ) helps manage this issue by removing excess sodium and water from your body. Here’s how it works:
How HCTZ Works in the Kidneys
HCTZ works on the distal convoluted tubule (DCT), a part of the kidney responsible for reabsorbing up to 10% of sodium into the bloodstream. By blocking this process, HCTZ prevents sodium from being reabsorbed. This causes more sodium to remain in the kidneys, which is eventually expelled as urine.
Sodium attracts water due to its osmotic properties, increasing urine production (diuresis). This helps eliminate excess fluid from your body and, in turn, helps lower blood pressure.
Why HCTZ Lowers Potassium Levels
Because sodium isn’t adequately reabsorbed earlier in the process, more of it reaches the later segments of the kidney, including the collecting ducts.
When there’s too much sodium in the collecting ducts, a hormone called aldosterone becomes active. Instead of letting sodium pass out in the urine, aldosterone signals the kidney to reabsorb sodium back into the bloodstream through specialized channels.
However, this reabsorption creates an electrochemical imbalance because sodium is a positively charged ion. To maintain this balance, the kidney compensates by exchanging another positively charged ion, which is potassium. Letting it pass out in the urine instead.
As this process continues, excessive potassium loss can occur, leading to hypokalemia, a condition characterized by low potassium levels in the blood.
Symptoms of Hypokalemia
Symptoms of hypokalemia vary depending on the severity of the condition. There are three stages:
| Stages | Potassium Level in the Blood |
| Mild hypokalemia | 3.0 – 3.5 mEq/L |
| Moderate hypokalemia | 2.5 – 3.0 mEq/L |
| Severe hypokalemia | below 2.5 mEq/L |
Mild-to-moderate hypokalemia may be asymptomatic and can often be treated with oral potassium supplements and dietary changes. In contrast, severe hypokalemia can lead to life-threatening complications, such as:
- Irregular heartbeats
- Respiratory failure
- Kidney problems
Hypokalemia causes weakness that starts in the legs and progresses upward to the trunk and arms. It can also affect the breathing muscles, potentially leading to respiratory failure and death. Other symptoms may include:
- Nausea
- Vomiting
- Constipation
- Abdominal bloating
- Fatigue or lack of energy
- Heart palpitations or abnormal rhythms
- Tingling sensations
If you notice any of these symptoms, contact your healthcare provider immediately.
Factors Influencing Potassium Loss with HCTZ
The extent of potassium loss can vary depending on:
- Dosage of HCTZ
Hydrochlorothiazide comes in tablet or capsule form, with strengths of:
- 12.5 mg
- 25 mg
- 50 mg
If you’re just starting treatment, you will likely begin with a daily dose of 12.5 to 25 mg, adjusting up to 50 mg per day after 2 to 4 weeks if necessary. However, higher doses can lead to a greater risk of potassium loss.
In one study, more than half of the participants taking 50 mg daily experienced low potassium levels.
Another study compared two daily doses (12.5 mg and 112.5 mg) over one month. While both doses effectively lowered blood pressure, the higher dose caused a significant drop in potassium levels (by 0.7 mEq/L), whereas the lower dose had no impact on potassium.
- High Sodium, Low Potassium Intake
High sodium levels can increase the activity of aldosterone and contribute to potassium loss.
On average, Americans consume up to 3,400 mg of sodium daily, which is well above the federal guideline of less than 2,300 mg per day for teens and adults. Among adults with hypertension, 86% exceed the daily limit.
In contrast, potassium was identified as a nutrient of concern in the US because most people do not get enough of it in their diet.
- Concomitant Medications
Some medications may increase the risk of potassium loss because of how they work. When taken with HCTZ, their effects can add up, leading to a greater drop in potassium levels. These include:
- Corticosteroids (e.g., prednisone): These medications cause the body to retain sodium, which leads to increased potassium loss through urine.
- Beta-2 Agonists (e.g., albuterol): These drugs push potassium into the cells, reducing the amount available in the bloodstream.
- Amphotericin B: This antifungal medication, although infrequently used, can harm the kidneys, causing excessive potassium and magnesium loss.
- Loop Diuretics (e.g., furosemide): A black box warning states that these medications are potent and, at high doses, can cause excessive fluid loss along with important electrolytes, including potassium.
The use of these medications is sometimes necessary, even with HCTZ. Close monitoring is essential to prevent excessive potassium loss and its complications.
- Underlying Health Conditions
Many health conditions associated with high blood pressure can lead to potassium loss, including:
Chronic Kidney Disease (CKD)
CKD is when the kidneys are damaged for at least 3 months and can’t filter blood properly. As a result, extra fluid and waste build up in the body. According to the CDC, 1 in 5 adults with hypertension may have CKD.
People with CKD often have problems with potassium levels, which can be either too high (hyperkalemia) or too low (hypokalemia). Hyperkalemia affects 14%-20% of patients, while hypokalemia affects 12%-18%.
Heart Failure
Fluid retention is common in heart failure patients, making diuretics essential for managing and stabilizing the condition. However, diuretic resistance, affecting up to 50% of patients, is a frequent clinical challenge. This occurs when relief is insufficient despite using an appropriate diuretic dose.
To address this, thiazide diuretics are often added to loop diuretics as combination therapy. In a 2024 study, researchers found that adding HCTZ (a thiazide diuretic) to intravenous furosemide (a loop diuretic) effectively improved the body’s response to diuretics in acute heart failure.
However, both types of diuretics can cause hypokalemia.
Hyperaldosteronism
A condition where there is too much aldosterone. This hormone helps the body retain salt and water but also causes the kidneys to get rid of potassium, leading to hypokalemia.
There are two types of hyperaldosteronism:
- Primary hyperaldosteronism, also known as Conn syndrome
- Secondary hyperaldosteronism
Primary hyperaldosteronism, in particular, can be seen in at least 10% of people with hypertension. It’s even more common, over 20%, in those with treatment-resistant hypertension, especially those under 40 or with low potassium levels.
- Age and Gender
Older adults may experience more significant potassium loss due to age-related changes in kidney function and hormonal balance. Some studies suggest women might be more susceptible to HCTZ-induced hypokalemia.
Managing Potassium Levels While on HCTZ
Taking steps to maintain potassium levels can help prevent complications while on hydrochlorothiazide. Here are some actionable strategies:
- Increase Potassium Intake
According to the National Academies of Sciences, Engineering, and Medicine (NASEM), the adequate intake for potassium is:
| Category | Adequate Intakes (mg) |
| Adult men | 3,400 |
| Adult women | 2,600 |
| Pregnant teens and women (ages 14-50) | 2,600 to 2,900 mg per day, depending on age |
| Breastfeeding teens and women (ages 14-50) | 2,500 to 2,800 mg per day, depending on age |
| Children (ages 1-18) | 2,000 to 3,000 mg per day, depending on age |
If you’re taking a medication like HCTZ, meeting or exceeding these guidelines through your diet becomes even more important. The American Heart Association (AHA) recommends consuming up to 5,000 mg of potassium per day.
Food sources high in potassium include:
- Potato
- Salmon
- Spinach
- Cantaloupe
- Milk
- Pinto beans
- Low-fat yogurt
- Banana
- Chicken breast
- Edamame
- Carrots
- Corn
- Raisins
- Broccoli
- Orange
- Strawberries
- Tomato
- Reduce Sodium Intake
The AHA recommends consuming no more than 2,300 mg of sodium per day. However, the ideal limit is 1,500 mg per day for most adults, especially those with high blood pressure. Reducing sodium intake by just 1,000 mg per day can help improve blood pressure and heart health.
To reduce sodium in your diet, choose fresh foods over processed or prepared ones whenever possible. When shopping, use the Nutrition Facts label to check sodium content and aim for products with 5% Daily Value (DV) or less (20% DV or more is considered high).
Additionally, look for nutrient claims on food and beverage packages to help identify options that are lower in sodium. Here’s a guide:
| Label | Description |
| Sodium-Free | Contains less than 5 mg of sodium per serving |
| Very Low Sodium | Contains 35 mg of sodium or less per serving |
| Low Sodium | Contains 140 mg of sodium or less per serving |
| Reduced Sodium | Contains at least 25% less sodium than the regular version of the product |
| Light in Sodium or Lightly Salted | Contains at least 50% less sodium than the regular version of the product |
| No Salt Added or Unsalted | No salt is added during processing, but these products might not be completely sodium-free unless specifically stated |
Source: FDA
- Consider Oral Potassium Supplements
To prevent hypokalemia in patients with ongoing potassium loss, such as those on diuretics or with hyperaldosteronism, the American Academy of Family Physicians (AAFP) recommends 20 mmol of potassium per day as usually sufficient.
An old study found that combining hydrochlorothiazide and potassium chloride (26 mmol) helped reduce blood pressure and prevent hypokalemia in individuals with essential hypertension.
For mild-to-moderate hypokalemia, 60 to 80 mmol per day over several days to weeks is typically enough.
Another old study on patients with hypertension, many of whom had hypokalemia due to HCTZ, tested three treatment plans combining HCTZ and potassium doses. All groups showed increased potassium levels within a week, which remained stable. However, the higher dose of potassium (40 mmol) was more effective than the lower dose (20 mmol).
| 🩺 Doctor’s Note Remember to consult your doctor first. Excessive potassium can lead to hyperkalemia (high potassium levels), which may cause: Weakness or fatigueIrregular heartbeatTingling or numbnessDifficulty breathing People with kidney disease are at higher risk of hyperkalemia because their kidneys may struggle to remove excess potassium. Follow your doctor’s advice to avoid complications. |
- Potassium Replacement (for severe cases)
In severe cases, potassium chloride replacement may be necessary for correcting hypokalemia, requiring a more aggressive approach. Treatment can involve oral or intravenous (IV) potassium, depending on the severity.
The preferred regimen is 40 mmol every 3 to 4 hours for three doses, administered orally, through IV, or both. Intravenous potassium is recommended in cases of:
- Cardiac dysrhythmias or irregular heartbeat
- Overdose from heart medications, specifically those containing digoxin or digitoxin
- Reduced blood flow to the heart
This ensures rapid correction when hypokalemia poses serious risks.
- Use a Potassium-Sparing Diuretic
Potassium-sparing diuretics block aldosterone or sodium channels, preventing the body from losing potassium while still removing sodium and water. Examples include:
- Amiloride (Midamor)
- Eplerenone (Inspra)
- Spironolactone (Aldactone, Carospir)
- Triamterene (Dyrenium)
A systematic review found that adding potassium-sparing diuretics to thiazide diuretics helps counteract potassium loss. It also showed that potassium-sparing diuretics reduce the blood sugar increase caused by thiazides alone, making the combination a better option for managing hypertension.
These medications are usually well-tolerated but require caution due to hyperkalemia, especially if you have kidney issues. Follow your doctor’s guidance for safe use.
- Monitor Your Levels Regularly
If you’re prescribed HCTZ, regular blood tests will likely be part of your care plan. These tests help track your electrolyte levels, including potassium.
In some cases, your doctor might recommend periodic electrocardiograms (ECGs) to ensure your heart rhythm remains stable, especially if your potassium levels are borderline low.
Alternatives to Hydrochlorothiazide
If maintaining potassium levels remains difficult despite dietary changes and supplementation, switching to a different medication may be an option. Some alternatives include:
Beta Blockers
Beta-blockers prevent adrenaline from entering cells, causing the heart to beat more slowly and with less force. This helps lower blood pressure. They are often prescribed when other medications, such as diuretics, have not been effective.
ACE Inhibitors
These drugs block the enzyme that converts angiotensin I into angiotensin II, which narrows blood vessels. By preventing this process, ACE inhibitors help blood vessels remain open, improving blood flow and reducing blood pressure and strain on the heart.
Angiotensin II Receptor Blockers
ARBs block the effects of angiotensin II, preventing blood vessel constriction. This allows blood vessels to remain open, making blood flow easier and helping to lower blood pressure.
Calcium Channel Blockers
These medications prevent calcium from entering the heart and blood vessel cells. This reduces blood pressure and, in some cases, slows the heart rate. Calcium channel blockers are also used for angina (chest pain) and heart rhythm disorders.
Alpha Blockers
These drugs block alpha receptors, which typically cause blood vessels to constrict. They are primarily used to treat high blood pressure and prostate enlargement (BPH) but are less commonly prescribed as first-line treatments for hypertension.
Discuss these options with your healthcare provider if you experience persistent potassium-related issues.
Final Thoughts
The severity of potassium loss while on HCTZ depends on factors like your age, gender, dosage, sodium intake, other medications you’re taking, and any underlying health conditions.
Recognizing the signs such as muscle weakness and fatigue is essential for early intervention. If you’re taking HCTZ, you can help maintain healthy potassium levels by increasing your dietary potassium intake, reducing sodium consumption, and considering supplements if necessary. In more severe cases, potassium replacement therapy may be required.
Regular monitoring of your electrolyte levels can help prevent complications and ensure that your treatment remains safe and effective. Always consult your healthcare provider to find the best approach for your needs.
FAQs About HCTZ and Potassium Levels
Can hydrochlorothiazide cause high potassium levels instead of low potassium?
Hydrochlorothiazide usually lowers potassium levels but may rarely cause high potassium in individuals with kidney disease, those taking potassium-sparing medications, or those consuming excessive potassium supplements.
Is it safe to take hydrochlorothiazide and losartan potassium together for high blood pressure?
Yes, hydrochlorothiazide and losartan potassium are commonly prescribed together for high blood pressure, as losartan helps counteract potassium loss caused by hydrochlorothiazide. This combination is generally safe and is available as a single medication, such as Hyzaar. However, potassium levels should be monitored because losartan can increase the risk of hyperkalemia, especially in individuals with kidney disease or other risk factors.
Sources
- Lin, Z., Li, H. L., Tsoi, M. F., & Cheung, B. M. Y. (2022). Hypokalaemia associated with hydrochlorothiazide used in the treatment of hypertension in NHANES 1999–2018. Journal of Human Hypertension, 37(5), 354–362. https://doi.org/10.1038/s41371-022-00704-x
- Schnaper, H. W. (1989b). Potassium restoration in hypertensive patients made hypokalemic by hydrochlorothiazide. Archives of Internal Medicine, 149(12), 2677. https://doi.org/10.1001/archinte.1989.00390120043009
- McKenney, J. M., Goodman, R. P., Wright, J. T., Rifai, N., Aycock, D. G., & King, M. E. (1986). The effect of Low‐Dose hydrochlorothiazide on blood pressure, serum potassium, and lipoproteins. Pharmacotherapy the Journal of Human Pharmacology and Drug Therapy, 6(4), 179–184. https://doi.org/10.1002/j.1875-9114.1986.tb03473.x
- Gilligan, S., & Raphael, K. L. (2017). Hyperkalemia and hypokalemia in CKD: prevalence, risk factors, and clinical outcomes. Advances in Chronic Kidney Disease, 24(5), 315–318. https://doi.org/10.1053/j.ackd.2017.06.004
- Horiuchi, Y., & Wettersten, N. (2024). Treatment strategies for diuretic resistance in patients with heart failure. Journal of Cardiology. https://doi.org/10.1016/j.jjcc.2024.06.005
- Shams, E., Bonnice, S., & Mayrovitz, H. N. (2022). Diuretic Resistance Associated With Heart Failure. Cureus, 14(1), e21369. https://doi.org/10.7759/cureus.21369
- Sánchez-Marteles, M., Garcés-Horna, V., Morales-Rull, J. L., Casado, J., Carrera-Izquierdo, M., Conde-Martel, A., Dávila-Ramos, M. F., Llácer, P., Salamanca-Bautista, P., Ruiz, R., Aramburu-Bodas, O., Formiga, F., Manzano, L., & Trullàs, J. C. (2024). Combining loop and thiazide diuretics across the left ventricular ejection fraction spectrum. JACC Heart Failure, 12(10), 1719–1730. https://doi.org/10.1016/j.jchf.2024.05.006
- Lin, Z., Wong, L. Y. F., & Cheung, B. M. Y. (2021). Diuretic-induced hypokalaemia: an updated review. Postgraduate Medical Journal, 98(1160), 477–482. https://doi.org/10.1136/postgradmedj-2020-139701
- Andersen, B., Snorrason, S. P., Ragnarsson, J., & Hardarson, T. (1985). Hydrochlorothiazide and Potassium Chloride in Comparison with Hydrochlorothiazide and Amiloride in the Treatment of Mild Hypertension. Acta Medica Scandinavica, 218(5), 449–454. https://doi.org/10.1111/j.0954-6820.1985.tb08873.x
- Martins, V. M., Ziegelmann, P. K., Ferrari, F., Bottino, L. G., Lucca, M. B., Corrêa, H. L. R., Blum, G. B., Helal, L., Fuchs, S. C., & Fuchs, F. D. (2023). Thiazide diuretics alone or combined with potassium-sparing diuretics to treat hypertension: a systematic review and network meta-analysis of randomized controlled trials. Journal of Hypertension, 41(7), 1108–1116. https://doi.org/10.1097/hjh.0000000000003436