Acidosis is a condition where your blood becomes too acidic, dropping below its normal pH of 7.35. Healthy blood stays in a narrow range between 7.35 and 7.45, which is slightly basic. When something disrupts that balance, whether a lung problem, a kidney issue, or a buildup of acid from another source, the result is acidosis. Left untreated, severe cases can lead to shock or death, but most forms are manageable once the underlying cause is identified.
How Your Body Manages Acid
Your body constantly produces acid as a byproduct of normal metabolism. Two systems work together to keep blood pH stable: your lungs and your kidneys. The lungs regulate acid levels by controlling how much carbon dioxide you exhale. Carbon dioxide is acidic when dissolved in blood, so breathing faster or deeper removes more of it. The kidneys take a slower approach, filtering excess acid out of the blood and into urine while recycling bicarbonate, a natural base that neutralizes acid.
When one system falters, the other tries to pick up the slack. If your kidneys allow too much acid to accumulate, your lungs compensate by increasing your breathing rate to blow off more carbon dioxide. If your lungs retain too much carbon dioxide, your kidneys respond over several hours by holding onto more bicarbonate. This cross-compensation is why acidosis sometimes develops slowly and without obvious symptoms: the backup system is masking the problem.
Metabolic Acidosis
Metabolic acidosis happens when your body either produces too much acid or your kidneys fail to remove enough of it. Doctors distinguish between two patterns based on something called the anion gap, which is the difference between positively and negatively charged particles in your blood. A large gap suggests extra acid is being dumped into the bloodstream. A normal gap points to a loss of bicarbonate instead.
Several conditions cause a high anion gap. Diabetic ketoacidosis occurs when uncontrolled diabetes forces the body to break down fat for energy, releasing acidic byproducts called ketones. Lactic acidosis develops when your tissues don’t get enough oxygen, prompting muscles and red blood cells to produce lactic acid. This can result from liver failure, low blood sugar, alcohol use disorder, cancer, or even extremely intense exercise.
On the other side, normal anion gap acidosis typically involves losing bicarbonate directly. Severe diarrhea and overuse of laxatives are common triggers because they flush bicarbonate out of the body before it can do its job. Kidney disease can also cause this pattern when the kidneys lose the ability to reclaim bicarbonate or excrete acid properly.
Renal Tubular Acidosis
Renal tubular acidosis is a specific form of metabolic acidosis where the kidneys structurally can’t handle acid the way they should. There are three main types, each affecting a different part of the kidney’s filtering tubes. Type 1 involves a problem at the far end of the tubes, where acid is normally secreted into urine. Type 2 affects the beginning of the tubes, where bicarbonate is normally reclaimed. Type 4 occurs when the tubes can’t remove enough potassium, which interferes with their ability to excrete acid. All three types leave excess acid in the blood.
Respiratory Acidosis
Respiratory acidosis develops when your lungs can’t expel enough carbon dioxide. The carbon dioxide builds up in your blood, reacts with water, and forms carbonic acid. The core problem is always inadequate ventilation: air isn’t moving in and out of the lungs efficiently enough.
Chronic obstructive pulmonary disease (COPD) is the most common cause. In COPD, damaged air sacs create “dead space” in the lungs where blood flows but gas exchange doesn’t happen effectively. Sleep apnea is another frequent culprit, repeatedly pausing breathing during sleep and allowing carbon dioxide to accumulate. Sedating medications like opioids and benzodiazepines can slow breathing enough to trigger respiratory acidosis, as can conditions affecting the brain, nerves, or muscles that control breathing. Stroke, severe obesity, and an underactive thyroid can all reduce your body’s ability to regulate breathing properly.
Symptoms to Recognize
Mild acidosis often produces no obvious symptoms, which is part of what makes it dangerous. As it worsens, symptoms depend on the type.
Metabolic acidosis has a hallmark breathing pattern called Kussmaul breathing: rapid, deep breaths at a steady pace, sometimes described as “air hunger.” This is the lungs’ attempt to compensate by blowing off as much carbon dioxide as possible. When diabetic ketoacidosis is the cause, earlier signs include frequent urination, extreme thirst, and dehydration. More severe stages bring nausea, vomiting, abdominal pain, fruity-smelling breath, and profound fatigue.
Respiratory acidosis tends to present differently because the lungs are the problem rather than the solution. Headaches, confusion, drowsiness, and anxiety are common because rising carbon dioxide levels directly affect the brain. In severe cases, this can progress to disorientation or loss of consciousness.
How Acidosis Is Diagnosed
The primary tool is an arterial blood gas test, which measures three key values from a blood sample drawn from an artery (usually in your wrist). Normal reference ranges are:
- pH: 7.35 to 7.45. Below 7.35 confirms acidosis.
- Carbon dioxide pressure: 35 to 45 mmHg. A value above 45 suggests respiratory acidosis.
- Bicarbonate: 22 to 26 mEq/L. A value below 22 suggests metabolic acidosis.
By comparing these three numbers, doctors can tell whether the acidosis is metabolic, respiratory, or a mix of both, and whether the body’s compensation systems are working. An anion gap calculation from a separate blood panel helps narrow down the metabolic causes further.
How Acidosis Is Treated
Treatment always targets the underlying cause rather than just correcting the pH number. For diabetic ketoacidosis, that means insulin and fluids. For lactic acidosis, it means restoring oxygen delivery to tissues. For respiratory acidosis caused by COPD or another lung condition, improving ventilation is the priority, sometimes with supplemental oxygen or breathing support.
Bicarbonate, a base that directly neutralizes acid, is sometimes given intravenously for metabolic acidosis, but its use is more selective than you might expect. Clinical evidence supports it most clearly for acidosis caused by bicarbonate loss (like severe diarrhea), chronic kidney disease, and certain poisonings. For respiratory acidosis alone, bicarbonate is generally not recommended because the real fix is getting the lungs to clear carbon dioxide. In cases where both metabolic and respiratory acidosis overlap, creating dangerously low pH levels, bicarbonate may be used as a bridge to buy time while the root cause is addressed.
Chronic forms of acidosis, such as those caused by kidney disease or renal tubular acidosis, often require long-term management with oral bicarbonate supplements and treatment of the kidney condition itself. The goal is keeping blood pH stable enough to prevent complications from accumulating over time.