Anion Gap

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An anion gap test is performed to check the levels of ions (electrically charged particles) in your blood. This test can help your doctor or other medical personnel to diagnose the acid-base level in your body. The test results will be analyzed based on the electrolyte levels and other blood tests. Your blood contains sodium, chloride and bicarbonate — which contain electrically charged particles. An anion gap test also serves to help your doctor identify what other particles could make your blood neutral again.

This test can also provide hints about different types of acidosis when your blood has become too acidic. Your doctor will help reduce the alkalosis. Acidosis, in particular, may be life-threatening. Thus, it is important to identify the cause and treat it as soon as possible.

Metabolic acidosis may be caused when your body produces too much acid. For example, lactic acidosis may occur if you exercise too much. If you have diabetes, you may be given ketoacidosis as your body produces acids called ketones. Acidosis may also be produced from certain toxins, such as methanol and aspirin. Another cause of acidosis is losing too much bicarbonate. This can happen if you have severe diarrhea or a kidney condition that does not take up enough bicarbonate.

Purposes of Anion Gap Test

An anion gap test serves to detect levels of electrolyte balance in your body. This test is especially useful if your doctor suspects that you have an electrolyte imbalance (usually sodium or potassium) or an acid-base imbalance.

Who Needs Anion Gap Test?

You may require an anion gap test if you have symptoms of metabolic acidosis with the following symptoms: fatigue, shortness of breath, nausea and vomiting, fast heart rate, and low blood pressure. This test is most often performed for altered mental status, acute renal failure and other acute illnesses.

Cost Estimation for Anion Gap Test 

The anion gap test may vary — depending on the selected hospital or laboratory. 

For more details regarding the cost estimation for anion gap testing, contact Smarter Health

Pre-Anion Gap Test

You do not need special preparation for the anion gap test. If your doctor recommends taking other blood tests, you may need to fast (not eat or drink) for several hours before the test.

In addition, your doctor will tell you about certain types of food and drink to avoid before the test

You should also tell your doctor about the types of medicines you take, especially antibiotics, as they may affect the test results.

Your doctor will usually tell you if there are any special procedures or instructions to follow before performing the test.

During Anion Gap Test

The anion gap test procedure is no different from any other blood test. A blood sample will be taken using a needle from your arm, then the sample will be sent to the laboratory for testing.

The laboratory will take a close look at electrically charged minerals in your blood called electrolytes. These help keep your blood from becoming too acidic — or not acidic enough. Electrolytes can carry a positive or negative charge. The anion gap test measures how balanced these charges are.

Post-Anion Gap Test

After the test, you may have bruises in your arm or feel pain. You should not worry as this is perfectly normal and you only need to rest. Your doctor will let you go home after the test and you can carry out your normal activities.

Your doctor will call you to explain the results of the anion gap test. Keep in mind that even if your anion gap is high or low, it does not mean you have a serious health problem.  For example, an anion gap number between 3 and 10 is considered normal, but the normal range varies from person to person, and also depends on the method the laboratory uses.

Understanding Your Anion Gap Test Results

The normal range for the anion gap is about 3 to 10 mEq / L (average six mEq / L), but may vary based on the method used by the laboratory to do the test. It should be noted that when calculating the anion gap, the CO2 value from your metabolic panel is often used as the equivalent value for HCO3- of arterial blood gases.

The total CO2 content includes serum bicarbonate as well as carbon dioxide, and serum HCO3 – comprises about 95% of the total CO2. Therefore, this measurement is usually done to estimate HCO3 levels.

If your results show a high anion gap, you may have acidosis — which means you have higher than normal acid levels. Acidosis may be a sign of dehydration, diarrhea, or too much exercise. It may also indicate a more serious condition such as kidney disease or complications of diabetes. Acidosis may also be caused by too much exercise.

If your results show a low anion gap, you may have low levels of albumin — a protein in the blood. Low albumin may indicate kidney problems, heart disease, or certain types of cancer. Since low anion gap results are rare, retesting is usually recommended to provide more accurate results. 

If you are diagnosed with a certain condition based on high or low anion gap test results, your doctor may recommend follow-up treatment. 

Some of the possible treatments for metabolic acidosis include detoxification (if it is caused by medicines or toxins) and insulin (if the condition is caused by diabetes).

Hemodialysis is required for renal failure and ethylene glycol, methanol, and salicylate poisoning. When metabolic acidosis results from loss of bicarbonate, such as in normal anion gap acidosis — bicarbonate therapy is usually highly recommended as it is safe and effective.

However, treatment with sodium bicarbonate for high anion gap acidosis is controversial as it is usually only used in cases of severe metabolic acidosis when the bicarbonate is very low and the pH is below 7.1.

Risks of Anion Gap Test

Taking a blood sample using a needle carries risks such as bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain.

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