Signs and symptoms of hypokalemia

From the desk of
Robb Wolf
ScienceSigns and symptoms of hypokalemia

Low serum potassium is no joke. The signs and symptoms of hypokalemia include cardiac arrhythmias, slower heart rate, muscle paralysis, and brain damage.

Hypokalemia is fairly common in hospitals, but fairly rare otherwise. Without the influence of medical conditions, illness, and medications, the human body maintains potassium levels like a champ.

Eating a low-potassium diet won’t make you run out of potassium. You still have plenty of potassium stored in your skeleton, and your body is glad to deplete these potassium reserves to prevent hypokalemia. This is one reason why low potassium diets are linked to osteoporosis. It’s also why low potassium intakes won’t manifest as hypokalemia on a blood test.

Most people don’t get this. They think if serum potassium levels come back normal, they’re all set with potassium. But that’s not how it works. Hypokalemia is one thing. Simple potassium deficiency is another.

The symptoms of moderate to severe hypokalemia are serious and urgent. They generally require medical intervention to rapidly restore potassium levels.

The symptoms of potassium deficiency are more subtle. Do you monitor your blood pressure daily? Do you check your bone mineral density? Most people don’t, but high blood pressure and brittle bones are consequences of a low potassium diet. Over the course of a lifetime, these consequences can be devastating.

I’m not trying to frighten you into buying the nearest potassium powder. (Most of your potassium should come from food anyway.) I just want to provide useful info so you can make better decisions about your health.

Anyways, back to the point. Today I’ll be talking about both hypokalemia and potassium deficiency. Once we differentiate between the two, we can move on to optimizing potassium status.

What Is Hypokalemia? (And Why Potassium Matters)

Hypokalemia is a medical condition of low serum potassium. According to NIH StatPearls, someone is considered hypokalemic when blood potassium levels fall below 3.4 millimoles per liter (mmol/L).

Low potassium levels are further stratified as follows:

  • Mild hypokalemia: 3 to 3.4 mmol/L
  • Moderate hypokalemia: 2.5 to 3 mmol/L
  • Severe hypokalemia: less than 2.5 mmol/L

Hypokalemia is more common than its sister electrolyte disturbance: hyperkalemia. I won’t spend much time on high potassium levels today, but the underlying causes (kidney issues, injury, or medications) are often similar.

When you think of hypokalemia, think of heart problems. Potassium is crucial for heart function, and low serum potassium can cause dysrhythmias, bradycardia (slow heart rate), and other electrical disturbances.

But potassium doesn’t just influence the energetics of the heart. It influences every cell in your body.

Every cell in your body contains sodium-potassium pumps that pump sodium and potassium ions through the cell membrane. Why must sodium and potassium be pumped? To regulate the cell’s membrane potential.

This electrical regulation allows cells to communicate. Cells need to communicate. It’s how anything gets done: breathing, moving, thinking, digesting, you name it. It all happens because cells talk to other cells.

When potassium levels fall, cells have trouble talking to other cells. And so you have heart problems, muscle weakness, paralysis, and so on. That’s how hypokalemia presents, so let’s talk more about those symptoms now.

Symptoms of Hypokalemia

Since I’ve called this blog “signs and symptoms of hypokalemia”, I should probably make good on that promise. The symptoms of mild hypokalemia include:

  • Muscle cramps
  • Lethargy
  • Tiredness
  • Constipation
  • Muscle weakness
  • Feeling lousy or “off”

These can also be symptoms of severe potassium deficiency. But as I mentioned earlier, potassium deficiency doesn’t generally show up in the blood or cause symptoms.

As potassium levels continue to fall, the symptoms get worse. The symptoms of moderate to severe hypokalemia include:

  • Slower heart rate
  • Cardiac arrhythmias
  • Severe muscle weakness
  • Various electrical disturbances of the heart
  • Brain damage
  • Problems regulating glucose
  • Rhabdomyolysis (muscle breakdown that damages the kidneys)
  • Structural or functional kidney disturbances
  • Polyuria (a large amount of dilute urine)
  • Muscle paralysis

Now that we’ve covered symptoms, let’s move on to causes.

What Causes Hypokalemia?

When someone develops hypokalemia, it’s usually because they lost excessive potassium through urine, stool, or vomit. It’s not because they weren’t eating enough potassium. Provided a person has healthy kidneys—and provided that person doesn’t have a potassium-depleting medical condition, illness, or drug profile—that person is at low risk for hypokalemia.

About 21% of hospitalized patients are hypokalemic. One big reason: many of these patients take diuretic medications that accelerate urinary potassium losses or laxative medications that accelerate gut potassium losses.

Speaking of gut health, any condition that causes diarrhea—cholera, Crohn’s disease, IBS, ulcerative colitis, gastroenteritis, etc.—will increase hypokalemia risk. Gut disorders also impair potassium absorption, creating a double whammy situation for low potassium.

Vomiting can also cause hypokalemia. Vomit itself contains potassium, plus the loss of stomach acid increases your body’s PH. To compensate, you excrete more potassium (an alkaline mineral) to re-acidify your body. Another double whammy.

Moving on, we come to refeeding syndrome. During periods of prolonged starvation, the body struggles to maintain serum potassium levels. But when the starved person finally eats, the body gets excited about rebuilding muscles and organs—and so it aggressively sends electrolytes (including potassium) out of the serum and into the tissues. Hello hypokalemia.

This last cause I’ll mention doesn’t get much airplay. Heard of PICA? It’s a psychological disorder in which the patient (oftentimes a kid) may eat clay, dirt, paper clips, hairballs, utility bills, and otherwise… Some of these materials can bind to potassium and block its absorption. An incredibly difficult disorder to contend with, and with unforeseen consequences.

Understanding Potassium Status

Potassium deficiency isn’t the same as hypokalemia. I can’t stress this point enough. Potassium deficiency occurs when you don’t consume enough potassium for optimal health. Hypokalemia is when blood levels of potassium fall below a certain range.

To check for hypokalemia, you need only a blood test. From there, a medical professional will review your relevant symptoms and possibly run some more tests.

For example, the doctor may ask for a 24-hour urine collection to measure potassium excretion. If urinary potassium is too high, it suggests a kidney problem.

From there, you come up with a treatment plan: usually oral or IV potassium supplements. You might also address the underlying cause, but that’s beyond the scope of this blog.

You can’t check for potassium deficiency with a blood test. Remember: at low dietary intakes of potassium, your body activates its homeostatic potassium-retention program. Unfortunately, this program has some nasty side effects.

Signs of Potassium Deficiency

The hallmark of potassium deficiency is elevated blood pressure. Across the literature, lower potassium intakes are associated with higher rates of hypertension.

What’s going on here? One mechanism is that since potassium dilates blood vessels, it decreases blood pressure. Potassium also helps balance the effects of sodium on bp.

Osteoporosis is another sign of potassium deficiency. Some clinical trials even suggest that potassium supplements can improve bone density.

As you’ll recall, your skeleton is your potassium backup system. When potassium is low, your bones get raided. Potassium may also prevent the acidic conditions that degrade bone.

Finally, less potassium in the diet means more calcium in the urine. And higher urinary calcium means higher kidney stone risk.

Optimizing Potassium Status

To avoid hypokalemia, avoid excessive potassium losses. This isn’t always under your control, of course, and it’s wise to seek medical attention if you’re at risk.

Consuming adequate potassium won’t prevent hypokalemia, but it will reduce the risk. It will also reduce the risk of high blood pressure, kidney stones, and osteoporosis.

For most people, “adequate potassium” means getting around 3.5–5 grams daily, but it doesn’t hurt to shoot for the Institute of Medicine’s target of 4.7 grams per day. The US government used to recommend 4.7 grams, but in 2019 they reduced the DRI to about 3 grams per day. To my eye, however, the evidence for greater intakes still makes the most sense.

To determine your potassium intake, do a dietary analysis. (I like the Cronometer app.) If you’re short by one or more grams, you have two main options to bump it up:

  1. Eat more potassium-rich foods like spinach, avocados, potatoes, and tomatoes.
  2. Increase supplemental potassium. (LMNT contains 200 mg potassium per stick.)

Get to 3.5–5 grams/day, and you’ll be in the optimal range for potassium intake. Job well done!

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