Potassium is a major electrolyte and the body’s main intracellular cation. It helps maintain normal nerve signalling, muscle contraction, fluid balance, and healthy cardiovascular function. This page explains what potassium does, where to get it from food, what low or high potassium may look like, and when medical review matters.
Plain-English summary: potassium helps your cells fire properly. It works closely with sodium and magnesium to support muscle function, nerve communication, heart rhythm, fluid balance, and blood pressure regulation. Food-first potassium intake is usually the safest approach. Supplements are not something to play with casually.
Potassium helps generate the electrical gradients that let cells communicate. That matters most in nerves, muscles, and the heart. It also supports fluid distribution between the inside and outside of cells.
Most potassium lives inside cells, while most sodium sits outside them. That gradient is not a minor detail. It is part of how your body creates electrical activity, moves nutrients, and keeps tissue function stable.
When potassium drops too low or rises too high, muscles and the heart can misfire. That is why potassium disturbances matter clinically.
Potassium from whole foods is generally well absorbed. Fruits, vegetables, legumes, dairy, and potatoes are useful contributors. In practice, low potassium is often less about poor absorption and more about losses, low intake, or medication effects.
A higher-potassium, whole-food dietary pattern can help balance a high-sodium diet and support healthier blood pressure in many people with normal kidney function. That does not mean everyone should start taking potassium tablets. Food and supplements are not the same thing here.
Potassium is widely distributed in food. The best practical approach is to build it across the day rather than obsess over one “superfood”. Potatoes, legumes, dairy, leafy greens, avocado, tomatoes, citrus, and some fish can all help.
| Food | Typical serve | Approx. potassium | Why it matters |
|---|---|---|---|
| Baked potato, skin on | 1 medium | ~700–900 mg | One of the most useful everyday whole-food sources. |
| White beans / cannellini beans | 1 cup cooked | ~800–1000 mg | High-potassium, fibre-rich, and useful in plant-forward diets. |
| Lentils | 1 cup cooked | ~700–750 mg | Good staple source with protein and fibre. |
| Spinach | 1 cup cooked | ~800–850 mg | Dense source, especially when cooked down. |
| Avocado | 1 medium | ~700 mg | Useful for balanced meals and snacks. |
| Sweet potato | 1 medium cooked | ~500–600 mg | Practical whole-food source with carbohydrate. |
| Banana | 1 medium | ~350–420 mg | Popular, but not the only option and not the highest. |
| Tomato paste / tomato-rich dishes | 2–4 tbsp | ~300–600 mg | Potassium can add up fast in concentrated tomato foods. |
| Orange juice | 250 mL | ~450–500 mg | Useful in some contexts, but watch total sugar load. |
| Greek yoghurt | 200 g | ~250–350 mg | Modest but reliable contributor. |
| Salmon | 120 g cooked | ~450–600 mg | Adds protein plus useful potassium. |
| Coconut water | 250 mL | ~400–600 mg | Can help intake, but not automatically appropriate for everyone. |
Values are approximate and vary by variety, brand, ripeness, cooking method, and serve size. Cooked foods may concentrate or dilute potassium depending on preparation.
Low potassium can affect muscle and nerve function, and in more significant cases it can disturb heart rhythm. It is often caused by losses, not just low intake.
High potassium is not something to self-manage. It can become dangerous quickly, especially in people with kidney impairment, significant illness, or certain medicines.
Potassium status is usually checked with a serum potassium blood test, but interpretation needs context. A result can be distorted by haemolysis, dehydration, acid–base status, medicines, kidney function, or the timing of sample processing.
| Test / clue | What it shows | Why it matters |
|---|---|---|
| Serum potassium | Current blood potassium concentration | Main screening test, but not a full picture of total body potassium. |
| Haemolysis check | Whether the blood sample was damaged | Haemolysis can falsely raise potassium. |
| ECG | Electrical effects on the heart | Useful when potassium is significantly abnormal or symptoms are concerning. |
| Urinary potassium | Renal potassium handling | Can help distinguish renal losses from other causes in clinical assessment. |
| Kidney function tests | Renal capacity to regulate potassium | Critical when hyperkalaemia risk is present. |
| Magnesium | Related electrolyte status | Low magnesium can make hypokalaemia difficult to correct. |
Reference intervals vary by laboratory. Potassium results should be interpreted alongside symptoms, medicines, renal function, acid–base status, hydration state, and ECG findings where relevant.
Magnesium matters. If magnesium is low, correcting potassium can be more difficult. That is one reason electrolyte problems often need proper clinical assessment rather than one isolated supplement.
For most healthy people, improving dietary potassium through whole foods is the safer and more sensible approach. High-dose supplemental potassium is not a casual wellness product.
No. Bananas are fine, but they are not the whole story. Potatoes, legumes, avocado, cooked greens, tomato products, dairy, and some fish can all be strong contributors.
It can. Low potassium may contribute to weakness, muscle cramps, constipation, and abnormal heart rhythm, especially when the drop is more significant or ongoing.
Yes. High potassium can be serious, especially in people with kidney disease or those taking certain medicines. It can affect cardiac conduction and may require urgent medical care.
Not blindly. Cramps and fatigue can have many causes. Potassium supplements are not appropriate for everyone and can be risky in the wrong clinical setting. Food-first and proper assessment is the safer path.
Magnesium helps with potassium handling at the cellular and renal level. If magnesium is low, potassium can be harder to normalise. That is why electrolyte issues often need a broader review.
A potassium-rich whole-food diet can support healthier blood pressure regulation in many people with normal kidney function. That does not mean high-dose potassium supplements are a good idea for everyone.
TGA-compliant note: This page is educational and describes normal physiological roles, food sources, and evidence-informed safety considerations. It does not claim to diagnose, treat, cure, or prevent disease.