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What to Know About Acid-Base Balance

Medically Reviewed by Dan Brennan, MD on June 05, 2021

Your body must stick to a precise balance of acidity and alkalinity in order to function properly. Even a slight change in this balance can affect many organs.

What Is Acid-Base Balance?

The acidity and alkalinity of your blood are measured using the pH scale. The pH scale ranges from 0 (very acidic) to 14 (very alkaline). Blood is usually between 7.35 to 7.45. 

Controlling Your Acid-Base Balance

Every organ system in your body depends on pH balance. But your lungs and kidneys work to regulate it.

Acids are produced during the many chemical reactions that take place in each cell (cellular metabolism). Carbon dioxide is constantly being produced by your cells as they metabolize the oxygen and nutrients they need. 

Each time there’s a change in the acid-base balance, your body automatically pushes your blood pH level back to normal. But if your blood pH level changes significantly, then these automatic mechanisms aren’t working.

Lungs. Your brain controls how fast and how deeply you breathe. It regulates the amount of carbon dioxide you’re breathing out. When you breathe deeper and faster, you exhale more carbon dioxide and increase the pH of your blood. Your breathing, or respiratory, system can adjust the pH level of your blood in just minutes.

Kidneys. Your renal system can also adjust your blood pH level. Your kidneys are able to remove excess acids or bases. But this effect can take hours or days.

Chemical buffer systems. Your body also has chemical buffer systems — built-in weak acids and bases — that can easily be broken down. They work by adjusting your body’s proportions of acids and bases.

Your body’s other chemical systems involve proteins, hemoglobin, and phosphates. The phosphate buffer system helps regulate the pH level of your urine. Proteins help with pH regulation within cells.

Hemoglobin, the main protein inside your red blood cells, helps regulate pH there.

Acid-Base Disorders

Your blood may have too much acid. This results in acidosis. When your blood has too much base (too alkaline), this is known as alkalosis.

Acidosis and alkalosis aren’t diseases, but they provide health care professionals with a clue that you may have a serious health problem.

Acidosis

Respiratory acidosis. This happens when your lungs aren’t able to remove excess carbon dioxide, and it builds up in your body.

The causes of respiratory acidosis include:

Early symptoms of respiratory acidosis include:

Metabolic acidosis. This happens when your body produces too much acid or is unable to remove acids properly.

Causes of metabolic acidosis include:

  • Ingesting a poison or too much of a drug, such as methanol, antifreeze, or aspirin
  • Having an abnormal metabolism due to, for example, poorly managed Type 1 diabetes or an advanced stage of shock 
  • Losing too much base, as through a bout of diarrhea 
  • Not eliminating enough acid due to, for example, your kidneys not working normally

If your metabolic acidosis is mild, you may not have any symptoms. Otherwise, you may experience:

  • Fatigue
  • Nausea
  • Vomiting

How your body responds to acidosis may leave you feeling weak, drowsy, and confused. In severe cases, you may develop heart problems and a drop in blood pressure. This can lead to coma and death.

Alkalosis

This is when your body:

  • Has too much bicarbonate in the blood (metabolic alkalosis)
  • Loses acid 
  • Has low levels of carbon dioxide (respiratory alkalosis)

Respiratory alkalosis. This may be caused by hyperventilation or rapid breathing. Such breathing causes too much carbon dioxide to be removed from your body.

Hyperventilation may be due to:

  • Anxiety
  • Pain
  • Low levels of blood oxygen
  • Fever
  • Aspirin overdose

Metabolic alkalosis. This may be caused by:

  • Severe or prolonged vomiting, which causes stomach acids to be lost
  • Loss of too many fluids or electrolytes (like potassium or sodium), which affects your kidneys’ control of acid-base balance
  • Overactive adrenal glands
  • Certain diuretics
  • Eating too much baking soda (bicarbonate of soda)

Symptoms of alkalosis include:

  • Tingling in your fingers and toes, and around your lips
  • Twitching and cramps in your muscles
  • Irritability
  • Muscle spasms (for severe alkalosis)

Sometimes alkalosis may not cause any symptoms.

Diagnosis of Acid-Base Disorders

Your doctor may order blood tests to measure the pH and carbon dioxide levels in your blood. The blood sample is usually taken from an artery in your wrist. Blood from your veins isn’t as reliable as arterial blood when measuring blood pH.

For acidosis, your doctor may also measure the amount of bicarbonate in your blood. Other blood tests may be needed to find out the cause of your acidosis.

For alkalosis, your doctor may also measure electrolyte levels in your blood and urine.

Treatment for Acid-Base Disorders

Your doctor will work on reversing the cause of your acidosis or alkalosis. 

For metabolic acidosis, treatment depends on the cause. For example, your doctor may treat your Type 1 diabetes. If you have respiratory acidosis, your doctor will work on improving your lung function. You may need drugs that open your airways. If your breathing is badly impaired, you may need a mechanical ventilator to help you breathe.

For metabolic alkalosis, you may be given water and electrolytes while the cause is treated. For respiratory alkalosis, the first step is to give oxygen. Your doctor will then look for the cause and treat it.  

Show Sources

SOURCES:  

Hopkins, E., Sanvictores, T., Sharma, S. Physiology, Acid Base Balance. StatPearls Publishing. 2020.

Merck Manual: “Acidosis,” “Alkalosis,” “Overview of Acid-Base Balance.”

Nursing: “Understanding acid-base balance.”

Oregon State University: “26.4 Acid-Base Balance.”

Patel, S., Sharma, S. Respiratory Acidosis. StatPearls Publishing. 2021.

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