Lactic acidosis is a serious health condition classified as a form of metabolic acidosis. It occurs when lactic acid (more precisely, lactate along with associated hydrogen ions) accumulates in the bloodstream faster than the body can clear it. In normal circumstances, the body produces lactate when the energy levels are reduced, especially when oxygen levels in the blood are low (such as during intense physical exercise).
Typically, lactate production increases when tissues do not receive enough oxygen-rich blood (a state known as hypoxia). However, elevated lactate levels may also occur when the liver or kidneys are unable to metabolize it effectively. A mild to moderate increase in blood lactate is often referred to as hyperlactatemia. When this buildup becomes severe enough to lower blood pH below normal levels (pH < 7.35), it is defined as lactic acidosis.
What Happens During Lactic Acidosis?
The effects of lactic acidosis vary depending on its severity and underlying cause. In mild cases, such as those associated with intense physical exercise, the condition is temporary. During strenuous activity, the body produces more lactate, which may contribute to muscle fatigue and a burning sensation. In healthy individuals, the liver and kidneys rapidly clear this excess lactate once activity stops.
However, lactic acidosis becomes dangerous when the production of lactate is persistent or when clearance is impaired. This often occurs in serious medical conditions such as sepsis, shock, or organ failure. As lactate levels rise and blood pH falls, normal cellular processes are disrupted. If it is left untreated, this can lead to worsening metabolic imbalance, multi-organ failure, and potentially death.
Symptoms
Symptoms of lactic acidosis can range from mild to severe and often reflect both the acid-base imbalance and the underlying cause. Check some common symptoms below:
- Muscle cramps or pain
- Generalized body aches
- Rapid or deep breathing (a compensatory response known as Kussmaul respiration)
- Fatigue (extreme tiredness)
- Nausea and vomiting
- Weakness
- Drowsiness or decreased alertness
- Ataxia (loss of coordination)
- Confusion or delirium
- Oliguria (reduced urine output)
If lactic acidosis develops due to a serious underlying condition, additional symptoms may occur. These include:
- Hypotension (low blood pressure)
- Fever (commonly seen in infections like sepsis)
- Jaundice (yellowing of the skin and eyes, which indicates liver dysfunction)
- Hypothermia (low body temperature), particularly in advanced or severe illness
Causes
The causes of lactic acidosis are broadly categorized based on whether oxygen delivery to tissues is impaired.
Type A Lactic Acidosis
Type A lactic acidosis is the most common form and results from inadequate oxygen delivery to tissues (hypoxia or hypoperfusion). This leads to increased anaerobic metabolism and increased lactate production. The most common causes include:
- Severe pulmonary (lung) diseases that impair oxygen exchange
- Circulatory disorders that reduce blood flow
- Hemoglobin abnormalities that impair oxygen transport
- Shock (septic, hypovolemic, or cardiogenic)
- Severe or prolonged seizures
- Intestinal ischemia (reduced blood flow to the intestines)
- Carbon monoxide poisoning
Strenuous exercise can also temporarily cause Type A lactic acidosis, but this is usually short-lived and resolves quickly in healthy individuals.
Type B Lactic Acidosis
Type B lactic acidosis occurs due to certain health conditions that negatively affect the body’s ability to metabolize lactate. It is typically related to metabolic dysfunction, toxins, or underlying diseases that impair lactate clearance or cellular metabolism.
Type B1 (Associated with underlying diseases)
- Liver disease (reduced lactate clearance)
- Kidney disease
- Thiamine (vitamin B1) deficiency
- HIV/AIDS
- Cancer (particularly hematologic malignancies)
- Mitochondrial disorders
- Alcohol use disorder
- Diabetic ketoacidosis (DKA)
Type B2 (Drug- or toxin-induced)
- Excessive alcohol use or poisoning
- Cocaine
- Beta-adrenergic agonists (for example, inhalers used in asthma)
- Epinephrine (especially in high doses)
- Certain anesthetics (including Propofol, in rare cases such as Propofol infusion syndrome)
- Antibiotics (such as Linezolid)
- Metformin (usually in the presence of kidney dysfunction)
- Nucleoside reverse transcriptase inhibitors (used in HIV therapy)
- Cyanide or carbon monoxide poisoning
B3 Type (Congenital/metabolic causes)
These are rare inherited disorders affecting enzymes involved in metabolism:
- Pyruvate dehydrogenase deficiency
- Pyruvate carboxylase deficiency
- Disorders of oxidative phosphorylation (mitochondrial diseases)
- Glycogen storage diseases
- Methylmalonic acidemia
- Fructose-1,6-bisphosphatase deficiency
D-Lactic Acidosis
Most cases of lactic acidosis involve L-lactate, the form naturally produced and metabolized by human cells. However, a rare condition known as D-lactic acidosis involves the accumulation of D-lactate, which is produced by certain bacteria in the colon.
This condition typically occurs in individuals with short bowel syndrome, where undigested carbohydrates are fermented by intestinal bacteria, producing D-lactate. Unlike L-lactate, D-lactate is not efficiently metabolized by human enzymes, leading to accumulation in the bloodstream.
Symptoms of D-lactic acidosis may include confusion, slurred speech, and impaired coordination, sometimes resembling intoxication.
What Are The Potential Complications of Lactic Acidosis?
Lactic acidosis is a medical emergency when severe or untreated. As a result, it may cause some complications. Check some examples below:
- Cardiovascular complications – Hypotension, arrhythmias (irregular heart rhythms), and increased risk of cardiac arrest
- Acute kidney injury (which may progress to renal failure)
- Multi-organ dysfunction – These include liver failure and pancreatic injury
- Neurological impairment – Confusion, disorientation, seizures, or coma
- Respiratory failure – This complication usually occurs due to fatigue and the inability to maintain compensatory breathing
- Death
This is not an exhaustive list. The risk and severity of complications depend on the underlying cause and how quickly treatment is initiated.
Diagnosis
Lactic acidosis is typically diagnosed through laboratory testing. It is generally defined by:
- Blood lactate levels above 4 mmol/L
- Blood pH below 7.35
Check below also for the most common diagnostic tests:
- Comprehensive metabolic panel (CMP) – It is used to evaluate kidney function, electrolytes, and overall metabolic status
- Serum lactate test – Measures lactate concentration in the blood
- Anion gap calculation – Doctors often perform it to identify metabolic acidosis and determine its severity
- Arterial blood gas (ABG) – This is a specific test used to assess blood pH, oxygen levels, and carbon dioxide levels
Additional tests may be performed to identify the underlying cause.
Treatment
Treatment depends on the severity and underlying cause of lactic acidosis.
- Mild cases (such as exercise-induced) – Usually resolve with rest, hydration, and recovery.
- Moderate to severe cases – Require urgent medical treatment, which may include:
- Intravenous (IV) fluids
- Oxygen therapy
- Treatment of the underlying condition (for example, antibiotics for sepsis, insulin for DKA)
- In some cases, advanced interventions (such as dialysis)
Early detection and immediate treatment are critical to prevent life-threatening complications.
Frequently Asked Questions
What are the signs of lactic acidosis?
Common signs include nausea, vomiting, abdominal pain, muscle cramps, and rapid breathing. Seek emergency care immediately if you experience severe abdominal pain, confusion, loss of consciousness, persistent vomiting, or bluish discoloration of the lips or fingernails.
What does lactic acid buildup feel like?
It is often described as a burning sensation in muscles, along with rapid fatigue and a feeling of heaviness. Moreover, the symptoms may extend beyond muscles and may include breathing changes and systemic illness.
What conditions increase the risk of lactic acidosis?
These include:
- Diabetic ketoacidosis (DKA)
- Severe kidney or liver disease
- Sepsis
- Chronic obstructive pulmonary disease (COPD)
- Shock or severe infections
Can lactic acidosis be prevented?
In some cases, lactic acidosis can be prevented by managing underlying health conditions and avoiding known risk factors. For example, people with diabetes should carefully monitor their blood sugar levels to reduce the risk of diabetic ketoacidosis (DKA). Staying well-hydrated, avoiding excessive alcohol consumption, and following prescribed medication guidelines (especially Metformin) may also help reduce risk. However, not all cases are preventable, particularly those caused by severe illness such as sepsis or shock.
Is lactic acidosis always a medical emergency?
Not always. Mild, temporary increases in lactate, such as those caused by intense exercise, are common and usually resolve quickly without medical treatment. In general, lactic acidosis (where blood pH is significantly reduced) is considered a medical emergency, especially when it is associated with serious conditions, including infections, organ failure, or poisoning. Persistent or worsening symptoms should always be evaluated by a healthcare professional.
How quickly does lactic acidosis develop?
The onset of lactic acidosis depends on the underlying cause. For instance, if you develop an acute condition such as sepsis, shock, or toxin exposure, it can develop rapidly (within a few hours). In other cases, such as medication-related or chronic disease-associated lactic acidosis, it may develop gradually over several days. Early recognition and treatment are vital in more severe cases. Consult a healthcare provider for personalized guidance and risk assessment.
