What Is the Difference between Alkalosis and Acidosis?

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  • Written By: Wanda Marie Thibodeaux
  • Edited By: O. Wallace
  • Last Modified Date: 05 December 2019
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The primary difference between alkalosis and acidosis is that alkalosis places blood pH above normal, while acidosis places blood pH below normal. The levels of bicarbonate (HCO3) and carbon dioxide (CO2) vary as well, being influenced by whether the acidosis or alkalosis is respiratory or metabolic in nature. Metabolic alkalosis and acidosis connects to diseases or conditions impacting HCO3, while respiratory alkalosis and acidosis connect to diseases or conditions impacting CO2.

When people talk about pH or potential of hydrogen, they are talking about how acidic or alkaline a substance is. Blood normally has a very narrow pH range, which goes from 7.35 to 7.45. This is just above neutral, or a pH of 7. This range is optimal for metabolic processes and proper oxygen delivery, so anything outside of the normal range can result in health impairments. Alkalosis means that a person's blood pH has exceeded the upper range limit of 7.45, while acidosis means that a person's blood pH has fallen below the lower range limit of 7.35.


Blood pH is connected to the lungs and kidneys to a high degree, because these organs are responsible for disposing of CO2 and HCO3 or acid, respectively. The pH level with respiratory acidosis is low, but levels of CO2 and HCO3 are high. Respiratory alkalosis gives the exact opposite results, having a high pH with low C02 and HCO3. When acidosis is metabolic, pH, CO2 and HCO3 are low, but when alkalosis is metabolic, pH, CO2 and HCO3 are all high.

Looking only at respiratory alkalosis and acidosis, the causes are not the same. Respiratory alkalosis may stem from issues such as hyperventilation, fever, exercise, liver failure, or central nervous system problems. Acidosis that is respiratory in nature also can be from central nervous system problems, but it occurs because of traumas, blockages or diseases that inhibit breathing, as well.

Moving on to the causes of metabolic alkalosis and acidosis, metabolic alkalosis occurs through ingesting too much HCO3, diarrhea or vomiting and dehydration. Metabolic acidosis can occur with kidney failure, loss of HCO3 through diarrhea, diabetic or alcoholic ketoacidosis and overdoses of toxins such as too much aspirin.

Comparing these two conditions under the lens of symptoms, acidosis can be asymptomic or cause problems such as tiredness, nausea, headache and coma. The symptoms of alkalosis include cramping and weakness. Both conditions can be severe and thus warrant treatment, although mild cases are fairly easy to correct.


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Post 3

Can I tell if my body is in acidosis or alkalosis by doing a urine pH test?

I've been suffering from allergies, indigestion, joint pain and cramps lately. I've read that these are symptoms of alkalosis.

I want to know if this can be diagnosed with a urine test. And if it turns out that I have alkalosis, can I treat it myself or do I need to see a doctor?

Post 2

@burcinc-- It's not that difficult!

Just remember that in metabolic alkalosis, both pH and bicarbonate are high and in metabolic acidosis, both pH and bicarbonate are low.

Respiratory alkalosis and acidosis is a bit more complicated. In respiratory alkalosis, pH is high while carbon dioxide is low. And in respiratory acidosis, pH is low and carbon dioxide is high.

pH and bicarbonate or carbon dioxide levels are always the opposite of one another in alkalosis and acidosis. So if you can remember at least one of these, you can guess the other in the exam.

Post 1

I have the hardest time remembering the differences between respiratory and metabolic alkalosis and acidosis for exams! I hate this subject!

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