A deficiency of potassium (hypokalemia) can occur in people with chronic disease or as a result of the aging process. The most common problems associated with reduced potassium levels are hypertension, congestive heart failure, cardiac arrhythmias, depression, and fatigue. A variety of conditions can cause the loss of potassium from the body. The most common of these conditions are vomiting, diarrhea, and other gastrointestinal problems.

Hypokalemia can also be caused when too much water is taken in too quickly in conjunction with heavy perspiration -- for example, in an overzealous attempt to prevent dehydration during sports. This can affect marathon runners and other serious athletes.

Renal disease (such as acute renal failure) and diabetes, depending on the stage of either, can also cause fluctuations in the levels of potassium. Additionally, many medications can cause depletion of potassium. Examples include diuretics, cortisone, prolonged use of aspirin, and laxatives.

The most common symptom of potassium depletion is fatigue. Other symptoms of potassium deficiency include slow reflexes, muscle weakness, and dry skin. A quick loss of potassium could lead to cardiac arrhythmias.

Severe potassium deficiency symptoms include decreased heart rate, extreme muscle weakness, bone fragility and, if untreated, death. A low level of potassium can be determined with a blood test and can be treated with potassium supplements.

Increased levels of potassium in the blood is known as hyperkalemia. Some common causes of this are reduced renal (kidney) function, an abnormal breakdown of protein, and severe infection. If there is no pathological cause for increased potassium levels, the kidneys are able to handle a large amount of potassium, and prevent the blood levels from increasing.