What is an Anion Gap?

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  • Written By: Meshell Powell
  • Edited By: A. Joseph
  • Last Modified Date: 04 October 2019
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An anion gap test is part of an electrolyte test that is sometimes ordered by doctors. The results generally are obtained from a blood test, also referred to as a serum test. The results of the test will help the doctor determine the possibility of a condition commonly known as acidosis. The test measures the anion gap, which essentially is the difference between the level of negatively charged ions, or anions, and the level of positively charged ions, or cations, that are in the blood.

Acidosis is a medical condition that causes too much acid to build up in the body. This affects the pH balance in the body and can lead to a host of medical problems if left untreated. There are two primary forms of acidosis. These forms include metabolic and non-metabolic acidosis. The treatments vary depending on the type of acidosis present, so the anion gap test is a valuable tool for doctors.

If the test results are elevated, it could signify that the body is producing too much acid or is somehow compromised to the point of insufficient acid removal. This could cause symptoms such as fatigue, difficulty breathing, low blood pressure or a decrease in appetite. The doctor must then determine the reason for the elevated anion gap. Some possible causes include dehydration, diabetes or even certain medications or toxins. Abnormally high results often are seen in patients who are experiencing renal failure.


With an anion gap that is lower than normal, alkaloid overproduction is likely the issue. Alkaloids are among the chemicals naturally present in the human body. This often occurs in kidney disease and can be the result of sodium or potassium loss through the urine. Other conditions such as multiple myeloma, hyponatremia or hypoalbuminemia also could be the cause of the lowered anion gap values.

When interpreting the anion gap test results, other test results are considered as well, like an arterial blood gas test. In addition, a full blood count, including chloride and glucose, usually is performed. Acidity often can be detected through a routine urinalysis as well.

If the anion gap test reveals abnormal levels, treatment is based on finding the underlying cause. Oftentimes, the patient is required to undergo intravenous therapy in an effort to return the body's pH levels to a normal state. After these levels have been corrected and the situation is deemed to be non-emergency in nature, it becomes possible to treat the root cause of the abnormal results.


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Post 3

@healthy4life – The first time I heard of it was when I went to the doctor because I was so fatigued all the time. I really didn't do that much physical labor, so I didn't get it.

I had low blood pressure, too, and I didn't know why. He told me that I had an abnormal anion gap and I needed treatment.

I'm glad that he listened to me, because in the past, I've had doctors just ignore the fact that I'm tired all the time. They chalk it up to stress or laziness, but this doctor actually took this time to run a test and get some results.

Post 2

I think that the link between the acidity of urine and the anion gap can point toward the reason for a urinary tract infection. If your urine isn't very acidic, then it can harbor bacteria that cause these infections.

This is probably why eating acidic foods like pineapple and yogurt and drinking cranberry juice can prevent and sometimes even cure a urinary tract infection. You are making your urine more acidic, so the bacteria can't live in it.

Post 1

I've never heard of an anion gap or acidosis. I wonder if this type of test is rarely conducted, because I've been to the doctor a lot in my life, but I've never once heard mention of this.

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