MSD Manual

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James L. Lewis III

, MD, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham

Reviewed/Revised Jul 2023

Alkalosis is excessive blood alkalinity (a measure of blood pH) caused by an overabundance of bicarbonate in the blood or a loss of acid from the blood (metabolic alkalosis), or by a low level of carbon dioxide in the blood that results from rapid or deep breathing (respiratory alkalosis).

  • People may have irritability, muscle twitching, muscle cramps, or even muscle spasms.

  • Blood is tested to diagnose alkalosis.

  • Metabolic alkalosis is treated by replacing water and mineral salts such as sodium and potassium (electrolytes) and correcting the cause.

  • Respiratory alkalosis is treated by correcting the cause.

Blood pH

Acidity and alkalinity of any solution, including blood, is indicated on the pH scale, which ranges from 0 (strongly acidic) to 14 (strongly basic or alkaline). A pH of 7.0, in the middle of this scale, is neutral.

Blood is normally slightly basic, with a normal pH range of 7.35 to 7.45. Usually the body maintains the pH of blood close to 7.40.

Causes of Alkalosis

If too much bicarbonate in the blood, a loss of acid from the blood, or a low level of carbon dioxide in the blood overwhelms the body's acid-base control systems Control of Acid-Base Balance An important part of being healthy is for the blood to maintain a normal degree of acidity or alkalinity. The acidity or alkalinity of any solution, including blood, is indicated on the pH scale... read more , the blood will become alkalotic. Alkalosis is categorized depending on its primary cause as

  • Metabolic

  • Respiratory

Metabolic alkalosis

Metabolic alkalosis develops when the body

  • Loses too much acid

  • Gains too much base

For example, stomach acid is lost during periods of prolonged vomiting or when stomach acids are suctioned with a stomach tube (as is sometimes done in hospitals).

In rare cases, metabolic alkalosis develops in a person who has ingested too much base from substances such as baking soda (bicarbonate of soda).

In addition, metabolic alkalosis can develop when excessive loss of fluids and electrolytes (such as sodium or potassium) affects the kidneys' ability to maintain the blood's acid-base balance. For instance, loss of potassium sufficient to cause metabolic alkalosis may result from an overactive adrenal gland Hyperaldosteronism In hyperaldosteronism, overproduction of the hormone aldosterone leads to fluid retention and increased blood pressure, weakness, and, rarely, periods of paralysis. Hyperaldosteronism can be... read more or the use of diuretics (for example, thiazides, furosemide, or ethacrynic acid).

Respiratory alkalosis

Respiratory alkalosis develops when

  • Rapid, deep breathing (hyperventilation) causes too much carbon dioxide to be expelled from the bloodstream

Symptoms of Alkalosis

Alkalosis may cause

  • Irritability

  • Muscle twitching and cramps

  • Tingling in the fingers and toes and around the lips

Tingling (paresthesia) is a common complaint in hyperventilation due to anxiety. Sometimes alkalosis causes no symptoms at all. If the alkalosis is severe, painful muscle spasms (tetany) can develop.

Diagnosis of Alkalosis

  • Blood tests

  • Urine tests

A doctor evaluates a person's acid-base balance by measuring the blood pH and levels of carbon dioxide (an acid) and bicarbonate (a base) in the blood. To learn more about the cause of the alkalosis, doctors also measure levels of electrolytes in samples of blood and urine.

Treatment of Alkalosis

  • Treatment of cause

  • In metabolic alkalosis, replacement of water and electrolytes

  • In respiratory alkalosis, giving oxygen if necessary or providing calming reassurance to a person who is hyperventilating due to anxiety

Almost always, treatment of alkalosis is directed at reversing the cause. Doctors rarely simply give acid, such as hydrochloric acid, to reverse the alkalosis.

Metabolic alkalosis is usually treated by replacing water and electrolytes (sodium and potassium) while treating the cause. Rarely, when metabolic alkalosis is very severe, dilute acid is given intravenously.

In respiratory alkalosis, the first step is to ensure that the person has enough oxygen. The doctor then looks for a serious cause, such as an infection. If pain is causing the person to breathe rapidly, relieving the pain usually suffices.

When respiratory alkalosis is caused by anxiety or a panic attack, a conscious effort to relax and slow breathing may make the condition disappear. Calming reassurance and emotional support can help. Sometimes people try to slow down their breathing by breathing into a paper bag, which may help raise the carbon dioxide level in the blood as the person breathes carbon dioxide back in after breathing it out. However, this is not recommended because it may lead to other problems (for example, worsening heart or lung problems because of breathing less oxygen).

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