Symptoms Causes and Treatment of High or Low Anion Gap

Anion gap is a value derived from the results obtained of blood electrolyte test. Electrolytes are substances that are found naturally in the body. They play vital role in various functions of the body. Major electrolytes are sodium, chloride, potassium, bicarbonate, etc. These electrolytes are electrically charged. They are involved in balancing acid and alkali in blood.

Some electrolytes are positively charged and some are negatively charged. Positively charged are called cations (sodium, potassium) and negatively charged electrolytes (chloride, bicarbonate) are called anions. Anion gap is calculated as value of (sodium+potassium)-(chloride+bicarbonate). The anion gap can be normal, high and low. If the value of anion gap is too high or too low, it indicates something wrong in your body. The anion gap value is described in milliequivalent per liter (mEq/L).

If the doctor suspects of electrolyte imbalance in a patient, he recommends a blood electrolyte test. From this test anion gap can be easily calculated. Electrolyte imbalance can occur due to various reasons such as diarrhea, vomiting, starvation, fever, burns, infection etc.

Most common symptoms of electrolyte imbalance are drowsiness, dry skin, dry tongue, increased thirst, shortness of breath, weak pulse, confusion etc.

Causes of High and Low Anion Gap:

Normally the anion gap in a person ranges between 3 to 10 (mEq/L). Several conditions can produce imbalance in the pH level of blood resulting in abnormal anion gap. Let us know the reasons of high anion gap first.

Causes of high anion gap: High anion gap occurs when the blood is excessively acidic in nature. This means a person is suffering from acidosis. Conditions responsible for acidosis lead to high anion ion gap. These conditions are;

  • Diabetic ketoacidosis.
  • Kidney failure
  • Starvation for a prolonged period of time.
  • Diarrhea for several days.
  • Overdose of certain drugs such as salicylates, metformin etc.
  • Alcoholic ketoacidosis.
  • Constant exposure to certain organic compounds such as ethylene glycol, methanol, toluene, paraldehyde, carbon monoxide etc.
  • Build up of lactic acid in the body.
  • Increase of urea level in blood.
  • Thiamine deficiency
  • High level of phosphate in blood.

Symptoms of High Anion:

  • Nausea
  • Vomiting
  • Fatigue
  • Low blood pressure
  • Headache
  • Lack of appetite
  • Confusion

Causes of Low Anion Gap:

Low anion gap is rarely found. If the result derived from value of electrolyte suggests low anion gap, the test is usually repeated as there may be a laboratory error. Besides laboratory error, the other cause of low anion can be hypoalbuminemia. It is less amount of albumin in the body. Albumin is a type of protein. Low albumin level generally occurs due to inflammatory changes in the body. Hypoalbuminemia is found in conditions such as starvation, malnutrition, sepsis, post surgery, kidney disease, severe burns etc. Hypoalbuminemia is also considered to be a reason for low anion gap in people suffering from multiple myeloma.

There are certain other rare conditions that may have low anion gap. These conditions are:

  • Bromide intoxication: Bromide is present in many medicines such as sedative, drug for myasthenia gravis etc. High concentration of bromide can give false low anion gap because of its negative charge.
  • Lithium is given in certain psychiatric conditions. It has positive charge. If the concentration becomes high, it can give rise to low anion gap.

Symptoms of Low Anion Gap:

Usually there are no particular symptoms of low anion gap, symptoms are those of underlying cause that has given rise to low anion gap. These symptoms may be as follows:

  • Irregular heart beats.
  • Fatigue
  • Nausea
  • Vomiting
  • Confusion
  • Low blood pressure
  • Weakness in muscles.


Treatment of abnormality in anion gap is mainly based on addressing the underlying cause. In case of low anion gap, the first thing your doctor will suggest is to repeat serum electrolyte test. If the patient is taking certain medicines such as lithium or bromide containing medicine, he must talk with the doctor. In case of hypoalbuminemia, human serum albumin is administered through intravenous route in the body.

In case if high anion gap results from toxins or alcohol poisoning, patient may need detoxification therapy. He may have to be hospitalized to take the treatment.