Medicine For People!

November 2011: Potassium – Common Deficiency, Simple Fix

pieces of the pure metal known as potassium

pieces of the pure metal known as potassium

Potassium – Common Deficiency, Simple Fix

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Potassium – Common Deficiency, Simple Fix

Potassium – who needs it?  Seth, for one.  In last month’s newsletter I told you the story of Seth, who deferred my advice to take potassium, even though the usual meds weren’t controlling his high blood pressure.  Then one day he suddenly felt so dizzy and disoriented he went to the ER.  In the hospital they discovered his blood pressure was soaring and his potassium levels were dismal.  IV potassium brought his blood pressure down to a healthy level.  Long term solution?  By adding an inexpensive potassium supplement available in the grocery store, he was able to reduce his prescription medication while controlling his blood pressure.

Why did potassium work for Seth?  As I explained last month, potassium (along with other minerals) is necessary for the electrical spark of nerve impulses.  If we are deficient in potassium, our muscle and nerve cells become excitable or unreliable.  Even with a minor potassium deficiency, the muscle cells surrounding the arteries become tighter, which raises blood pressure.  When potassium levels are extremely high or low, nerves and muscle fail. 

Potassium Deficiency – What Goes Wrong?

More common than those extremes are less severe alterations in potassium levels.  Blood levels of potassium can be in the so-called "normal" range, but if there is inadequate potassium inside muscle cells, we can develop cramping, high blood pressure, irregular heartbeat, a tendency to stroke and, in general, an increased risk of death. 

Before you run screaming to the health food store, let’s be clear on "risk."  Let a twenty year get a bit low on potassium and double his risk of heart attack, which is close to zero to begin with, and twice that is still just about zero.  When that twenty year old hits seventy, then double the risk becomes a bigger deal.

Potassium Deficiency is Common

Potassium is low in the modern diet compared to the fare on which we evolved.  Most often people just consume too little potassium and too much sodium.[1]. Other causes of potassium deficiency include:

  • Medications such as diuretics (the fluid pills prescribed for blood pressure);
  • Diarrhea or vomiting;
  • Magnesium deficiency (dietary magnesium is similarly low in the developed world, and magnesium is required for potassium transport through the membrane and into the cell);
  • Various hormonal illnesses.

A Special Note about Magnesium

About a third of Americans run low in magnesium, for much the same reasons they run low in potassium.  Magnesium deficiency still frequently eludes diagnosis.  If we are low in magnesium, the pumps in our cell membranes that concentrate potassium inside the cell don’t work.  And we can take all the potassium we want, to the point of dangerous over-dosage, and it won’t get inside the cell where we need to have it.  That’s why your doctor will usually ask you to take a magnesium supplement along with prescribed potassium.

The Problem with Blood Levels

Should you have your potassium blood levels tested?  Unless you have a deficiency as severe as Seth’s, that may not tell you much.  Since 90 percent of our potassium resides inside our cells[2], blood levels (which are extracellular) measure only the tip of the iceberg.  While the lab report may say that potassium levels between 3.5 and 5.2 millimoles per liter are normal, people with high blood pressure or irregular heartbeat should be at 4.0 as a minimum, and preferably above 4.5.   Some cardiologic authorities find this to be true for people with heart failure[3] as well, and report that maintaining optimal blood levels of potassium is the "most effective and safe antiarrhythmic intervention" in heart failure. 

Let’s Get Technical: What is a millimole?

You’ll note in the last paragraph the introduction of the term "millimole," signifying a thousandth of a mole, using the word mole in its chemical sense.


While potassium in foods usually is recorded by milligram weight of pure potassium, you cannot eat pure potassium.  You have to take potassium combined with something else. So we must prescribe potassium supplements and medications using millimole measures, Again, using milligram units can lead to dangerous errors. 

That is just one reason not to treat a presumed potassium deficiency on your own.

Potassium and Longevity

Researchers from the Centers from Disease Control, Harvard, and Emory Medical Schools surveyed[4] more than 12,000 adults over a period of some fifteen years.  They found those people with higher potassium intakes lived longer.  They died at just 80 percent the rate of those with the lowest intakes.  In other words, those who had good potassium intake experienced a 20 percent reduction in their overall death rate.

We are not talking here about a single study.  Nutrition workers around the globe repeatedly survey sodium and potassium intake.  Reliably, consistently, people with higher potassium intake have fewer strokes, fewer heart attacks, and longer lives.[5] [6] [7]

Potassium and High Blood Pressure

Some doctors, including myself, frequently recommend potassium for people with elevated blood pressure.  When we see people in our office with high blood pressure and low potassium, we can sometimes keep them from needing any medication by simply supplementing with potassium. 

As well, since doctors frequently start high blood pressure treatment with diuretics, and most diuretics make us lose potassium, we just cannot treat high blood pressure and ignore potassium!

Examining the Examiners

While there seems to be a serious movement afoot in this great land to be sure that we all die with a normal blood pressure, don’t get caught up just on the number.   In this newsletter on potassium I want to direct your attention to the real issue, prevention of strokes, heart attacks, and premature death. 

One of our mantras in Medicine for People! is caveat emptor. 

  • Be careful what you buy, medications and supplements are not all created equal.
  • Be careful what medical providers you choose, they are not all created equal.
  • Finally, be careful what medical information you accept.  Some of it can mislead you.

For example, gather information as I did on potassium and the problem of high blood pressure, stroke, and heart attack, and you will find one lonely review claiming that potassium does not work.  See my critique of that review here. Most published studies in which adequate potassium is given to people with high blood pressure do show a reduction in blood pressure after a few months, as well as a reduction in stroke.  Further, any given person with high blood pressure will not respond well to every blood pressure medication.  Standard practice is to give people medications and proceed depending upon their response.  Why should we treat nutrients any differently?   

Medical Benefits

Seth had extremely low levels of potassium and was already on medication, so he benefited very quickly.  For most people, up to four months of treatment is required before we see results.  We usually prescribe magnesium at the same time.  Potassium also can be helpful in treating irregular heart beat and muscle spasm or cramping. 

How Much Potassium do People Normally Consume?

Here are some numbers:

  • The recommended daily allowance is 4000 mg/day.  
  • Primitive humans consumed about 6000 mg/day.
  • Many African Americans get by on intakes of about 1000 mg/day.   Every doctor knows African-Americans are particularly prone to high blood pressure.   Could their low potassium intake play a role?
  • About 20 percent of all Americans get as little as 2400 mg/day.
  • Urban whites typically consume approximately 2500 mg/day.
  • Contemporary humans eating large amounts of fruits and vegetables tend to have an intake of approximately 8000 to 11000 mg/day.[8]

Who Should Not Take Potassium Supplements?

Unless monitored by your physician, you shouldn’t take potassium along with medications of the ACE inhibitor family.  Brand names are Lotensin, Capoten, Vasotec, Monopril, Prinivil, Zestril, Univasc, Accupril, Aceon, Altace and Mavik.  Generic names include benazepril, captopril, cilazapril, enalapril, fosinopril, lisinopril, moexipril, perindopril, quinapril, ramipril and trandolapril. (ACE inhibitor drugs have generic names that end in –pril.)

Unless monitored by your physician, you shouldn’t take potassium along with angiotensin II receptor blockers. Brand names include Atacand, Teveten, Avapro, Cozaar, Benicar, Micardis, and Diovan.   Generic names are candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, and valsartan.   (Angiotensin II receptor blockers have generic names ending in –sartan.) 

The combination with these drugs with supplemental potassium can result in dangerously elevated levels of potassium.   Still, some people on these medications still need supplemental potassium, which is why your doctor needs to be involved in the decision.

Drugs with a lower potential to increase potassium are beta-blockers, alpha-blockers, spironolactone, triamterene, amiloride, albuterol inhalers for asthma, indomethacin, ibuprofen, trimethoprim-sulfamethoxazole, heparin, and others.

Don’t take potassium if you have kidney failure! 

When kidney function falls far enough, the kidney allows potassium levels to rise, which can cause fatal arrhythmias of the heart.  Many people with kidney problems take medications to reduce potassium in the blood.  We always check kidney function before prescribing potassium.

How to Get Enough Potassium

Assuming you have healthy kidneys, there are two safe ways to maintain healthy potassium levels:

  • Eat potassium-rich foods
  • Use a salt substitute (these are about 99 percent potassium chloride) on your food instead of regular table salt.  You can buy inexpensive salt substitutes at the grocery store.

Potassium in Foods

Evidence indicates that people eating more potassium-rich foods require much fewer blood pressure medications to achieve a normal reading.[9]  You can see a listing of high-potassium food here.  Although potassium is present in our food, if potassium is low or if your doctor thinks you need extra potassium, you need to take potassium supplements.


Serving size

 Milligrams potassium per serving

orange juice

8 oz


prune juice

8 oz


tomato juice

8 oz



1/2 cup


potato baked with skin

1 each



1 each



3.5 oz



1 each



1 medium



1/2 cup



8 oz



8 oz



8 oz


Potassium in Supplements

For your safety, over-the-counter potassium tablets can contain no more than 99 milligrams per tablet.  The same holds true for multiple vitamins.

Because potassium excess can be fatal, you need to talk about potassium supplements with your physician.  However, unless he or she has advised you otherwise, feel free to consume a diet rich in fruits and vegetables.  You’ll have less reason to see your doctor if you do!

Read more about potassium.

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[1] Canadians continue to consume too much sodium and not enough potassium.  Tanase CM, Koski KG, Laffey PJ, Cooper MJ, Cockell KA.

Can J Public Health. 2011 May-Jun;102(3):164-8.

[2] Arch Intern Med. 2000;160:2429-2436

[3] Arch Intern Med. 2000;160:2429-2436

[4] Arch Intern Med. 2011;171(13):1183-1191


Editorial comment at

Sodium and potassium intake: mortality effects and policy implications: comment on "Sodium and potassium intake and mortality among US adults".  Silver LD, Farley TA.

Arch Intern Med. 2011 Jul 11;171(13):1191-2.  ND 1183

See also this previous study (same results).  High sodium-to-potassium ratio increases cardiac event risk. Study underscores the importance of balanced mineral intake.Heart Advis. 2009 Apr;12(4):5.

[5] Intersalt Cooperative Research Group. Intersalt: an international study of electrolyte excretion and blood pressure: results for 24-hour urinary sodium and potassium excretion. BMJ 1988;297:319-328

[6] In 1987, the results of a 12-year prospective population study (N=859) showed that the relative risk of stroke-associated mortality was significantly lower with higher potassium intake.13 In fact, multivariate analysis demonstrated that a 10-mmol higher level of daily potassium intake was associated with a 40% reduction in the relative risk of stroke mortality.

Potassium supplements was inversely related to the risk of stroke, particularly among hypertensive men.

The Joint National Committee for Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI) included increased potassium intake as a core recommendation for the prevention and treatment of hypertension.

The reduction of systolic blood pressure after potassium supplementation was approximately 3 times greater in blacks compared with whites.

Arch Intern Med. 2000;160:2429-2436

[7] Potassium, calcium, and magnesium intakes and risk of stroke in women.   Larsson SC, Virtamo J, Wolk A.

Am J Epidemiol. 2011 Jul 1;174(1):35-43. Epub 2011 May 3.

Division of Nutritional Epidemiology, National Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177 Stockholm, Sweden.

The authors examined the association between dietary potassium, calcium, and magnesium intakes and the incidence of stroke among 34,670 women 49-83 years of age in the Swedish Mammography Cohort who completed a food frequency questionnaire in 1997. The authors used Cox proportional hazards regression models to estimate relative risks and 95% confidence intervals. During a mean follow-up of 10.4 years (1998-2008), 1,680 stroke events were ascertained, including 1,310 cerebral infarctions, 154 intracerebral hemorrhages, 79 subarachnoid hemorrhages, and 137 unspecified strokes. There was no overall association between potassium, calcium, or magnesium intake and the risk of any stroke or cerebral infarction. However, among women with a history of hypertension, potassium intake was inversely associated with risk of all types of stroke (for highest vs. lowest quintile, adjusted relative risk = 0.64, 95% confidence interval (CI): 0.45, 0.92) and cerebral infarction (corresponding adjusted relative risk = 0.56, 95% CI: 0.38, 0.84), and magnesium intake was inversely associated with risk of cerebral infarction (corresponding adjusted relative risk = 0.63, 95% CI: 0.42, 0.93). Calcium intake was positively associated with risk of intracerebral hemorrhage (for highest vs. lowest tertile, adjusted relative risk = 2.04, 95% CI: 1.24, 3.35). These findings suggest that potassium and magnesium intakes are inversely associated with the risk of cerebral infarction among hypertensive women.

[8] Arch Intern Med. 2000;160:2429-2436

[9] Siani A, Strazzullo P, Giacco A, Pacioni D, Celantano E, Mancini M. Increasing the dietary potassium intake reduces the need for antihypertensive medication. Ann Intern Med 1991;115:753-759



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Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.