The several different causes of lactic acidosis include:

- Genetic conditions

- Biotinidase deficiency, multiple carboxylase deficiency, or nongenetic deficiencies of biotin

- Diabetes mellitus and deafness

- Fructose 1,6-bisphosphatase deficiency

- Glucose-6-phosphatase deficiency

- GRACILE syndrome

- Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes

- Pyruvate dehydrogenase deficiency

- Pyruvate carboxylase deficiency

- Drugs

- Linezolid

- Phenformin

- Metformin

- Isoniazid toxicity

- Propofol

- Propylene glycol (D-lactic acidosis)

- Nucleoside reverse transcriptase inhibitors

- Abacavir/dolutegravir/lamivudine

- Emtricitabine/tenofovir

- Potassium cyanide (cyanide poisoning)

- Fialuridine

- Other

- Impaired delivery of oxygen to cells in the tissues (e.g., from impaired blood flow (hypoperfusion))

- Bleeding

- Polymyositis

- Ethanol toxicity

- Sepsis

- Shock

- Advanced liver disease

- Diabetic ketoacidosis

- Excessive exercise (overtraining)

- Regional hypoperfusion (e.g., bowel ischemia or marked cellulitis)

- Cancers such as Non-Hodgkin's and Burkitt lymphomas

- Pheochromocytoma

Causes include:

The newest mnemonic was proposed in "The Lancet" reflecting current causes of anion gap metabolic acidosis:

- G — glycols (ethylene glycol & propylene glycol)

- O — oxoproline, a metabolite of paracetamol

- L — L-lactate, the chemical responsible for lactic acidosis

- D — D-lactate

- M — methanol

- A — aspirin

- R — renal failure

- K — ketoacidosis, ketones generated from starvation, alcohol, and diabetic ketoacidosis

The mnemonic MUDPILES is commonly used to remember the causes of increased anion gap metabolic acidosis.

- M — Methanol

- U — Uremia (chronic kidney failure)

- D — Diabetic ketoacidosis

- P — Paracetamol, Propylene glycol (used as an inactive stabilizer in many medications; historically, the "P" also stood for Paraldehyde, though this substance is not commonly used today)

- I — Infection, Iron, Isoniazid (which can cause lactic acidosis in overdose), Inborn errors of metabolism (an especially important consideration in pediatric patients)

- L — Lactic acidosis

- E — Ethylene glycol (Note: Ethanol is sometimes included in this mnemonic as well, although the acidosis caused by ethanol is actually primarily due to the increased production of lactic acid found in such intoxication.)

- S — Salicylates

Another frequently used mnemonic is KARMEL.

- K — Ketoacidosis

- A — aspirin

- R — Renal failure

- M — Methanol

- E — Ethylene glycol

- L — Lactic acidosis

Another frequently used mnemonic is KULT.

- K — Ketoacidosis (DKA, AKA)

- U — Uremia

- L — Lactic acidosis

- T — Toxins (Ethylene glycol, methanol, as well as drugs, such as aspirin, Metformin)

The preferred mnemonic of D. Robert Dufour, the chief of the Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center, is DUMPSALE, which omits the I of MUDPILES as the proposed values of *I* are exceedingly rare in clinical practice.

- D — Diabetic ketoacidosis

- U — Uremia

- M — Methanol

- P — Paraldehyde

- S — Salicylates

- A — Alcoholic ketoacidosis

- L — Lactic acidosis

- E — Ethylene Glycol

The mnemonic for the [rare, in comparison] toxins is ACE GIFTs: Aspirin, Cyanide, Ethanolic ketosis, Glycols [ ethylene and propylene ], Isoniazid, Ferrous iron, Toluene. Most of these cause a lactic acidosis.

The overall frequency of glycogen-storage disease is approximately 1 case per 20,000–25,000 people. Glycogen-storage disease type 0 is a rare form, representing less than 1% of all cases. The identification of asymptomatic and oligosymptomatic siblings in several glycogen-storage disease type 0 families has suggested that glycogen-storage disease type 0 is underdiagnosed.

The major morbidity is a risk of fasting hypoglycemia, which can vary in severity and frequency. Major long-term concerns include growth delay, osteopenia, and neurologic damage resulting in developmental delay, intellectual deficits, and personality changes.

Acid-base disturbances such as lactic acidosis are typically first assessed using arterial blood gas tests. Testing of venous blood is also available as an alternative. Normal results are as follows:

Causes of increased anion gap include:

- Lactic acidosis

- Ketoacidosis

- Chronic renal failure (accumulation of sulfates, phosphates, urea)

- Intoxication:

- Organic acids, salicylates, ethanol, methanol, formaldehyde, ethylene glycol, paraldehyde, isoniazid

- Sulfates, metformin

- Massive rhabdomyolysis

A mnemonic can also be used - MUDPILES

- M-Methanol

- U-Uremia (chronic kidney failure)

- D-Diabetic ketoacidosis

- P-Paraldehyde

- I-Infection, Iron, Isoniazid, Inborn errors of metabolism

- L-Lactic acidosis

- E-Ethylene glycol (Note: Ethanol is sometimes included in this mnemonic, as well, although the acidosis caused by ethanol is actually primarily due to the increased production of lactic acid found in such intoxication.)

- S-Salicylates

Though lactic acidosis can be a complication of other congenital diseases, when it occurs in isolation it is typically caused by a mutation in the pyruvate dehydrogenase complex genes. It has either an autosomal recessive or X-linked mode of inheritance. Congenital lactic acidosis can be caused by mutations on the X chromosome or in mitochondrial DNA.

Congenital lactic acidosis (CLA) is a rare disease caused by mutations in mitochondrial DNA (mtDNA) that affect the ability of cells to use energy and cause too much lactic acid to build up in the body, a condition called lactic acidosis.

Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. Several types of metabolic acidosis occur. The main causes are best grouped by their influence on the anion gap.

The anion gap can be spuriously normal in sampling errors of the sodium level, e.g. in extreme hypertriglyceridemia. The anion gap can be increased due to relatively low levels of cations other than sodium and potassium (e.g. calcium or magnesium).

When acidosis is present on blood tests, the first step in determining the cause is determining the anion gap. If the anion gap is high (>12 mEq/L), there are several potential causes.

High anion gap metabolic acidosis is a form of metabolic acidosis characterized by a high anion gap (a medical value based on the concentrations of ions in a patient's serum). An anion gap is usually considered to be high if it is over 12 mEq/L.

High anion gap metabolic acidosis is caused generally by acid produced by the body. More rarely, high anion gap metabolic acidosis may be caused by ingesting methanol or overdosing on aspirin. The Delta Ratio is a formula that can be used to assess elevated anion gap metabolic acidosis and to evaluate whether mixed acid base disorder (metabolic acidosis) is present.

The list of agents that cause high anion gap metabolic acidosis is similar to but broader than the list of agents that cause a serum osmolal gap.

Familial disorders

- Cystinosis

- Galactosemia

- Glycogen storage disease (type I)

- Hereditary fructose intolerance

- Lowe syndrome

- Tyrosinemia

- Wilson's disease

Acquired disorders

- Amyloidosis

- Multiple myeloma

- Paroxysmal nocturnal hemoglobinuria

- Toxins, such as HAART, ifosfamide, lead, and cadmium

Pyruvate dehydrogenase deficiency (also known as pyruvate dehydrogenase complex deficiency or PDCD) is one of the most common neurodegenerative disorders associated with abnormal mitochondrial metabolism. PDCD is an X-linked disease that shows heterogeneous characteristics in both clinical presentation and biochemical abnormality. The pyruvate dehydrogenase complex (PDC) is a multi-enzyme complex that plays a vital role as a key regulatory step in the central pathways of energy metabolism in the mitochondria.

In general, the cause of a hyperchloremic metabolic acidosis is a "loss of base", either a gastrointestinal loss or a renal loss.

- Gastrointestinal loss of bicarbonate ()

- Severe diarrhea (vomiting will tend to cause hypochloraemic alkalosis)

- Pancreatic fistula with loss of bicarbonate rich pancreatic fluid

- Nasojejunal tube losses in the context of small bowel obstruction and loss of alkaline proximal small bowel secretions

- Chronic laxative abuse

- Renal causes

- Proximal renal tubular acidosis with failure of resorption

- Distal renal tubular acidosis with failure of secretion

- Long-term use of a carbonic anhydrase inhibitor such as acetazolamide

- Other causes

- Ingestion of ammonium chloride, hydrochloric acid, or other acidifying salts

- The treatment and recovery phases of diabetic ketoacidosis

- Volume resuscitation with 0.9% normal saline provides a chloride load, so that infusing more than 3-4L can cause acidosis

- Hyperalimentation ("i.e.", total parenteral nutrition)

The most commonly seen form of PDCD is caused by mutations in the X-linked E1 alpha gene and is approximately equally prevalent in both males and females. However, a greater severity of symptoms tends to affect males more often than heterozygous females. This can be explained by x-inactivation, as females carry one normal and one mutant gene. Cells with a normal allele active can metabolize the lactic acid that is released by the PDH deficient cells. They cannot, however, supply ATP to these cells and, therefore, phenotype depends largely on the nature/severity of the mutation.

Without adequate metabolic treatment, patients with GSD I have died in infancy or childhood of overwhelming hypoglycemia and acidosis. Those who survived were stunted in physical growth and delayed in puberty because of chronically low insulin levels. Mental retardation from recurrent, severe hypoglycemia is considered preventable with appropriate treatment.

Hepatic complications have been serious in some patients. Adenomas of the liver can develop in the second decade or later, with a small chance of later malignant transformation to hepatoma or hepatic carcinomas (detectable by alpha-fetoprotein screening). Several children with advanced hepatic complications have improved after liver transplantation.

Additional problems reported in adolescents and adults with GSD I have included hyperuricemic gout, pancreatitis, and chronic renal failure. Despite hyperlipidemia, atherosclerotic complications are uncommon.

With diagnosis before serious harm occurs, prompt reversal of acidotic episodes, and appropriate long-term treatment, most children will be healthy. With exceptions and qualifications, adult health and life span may also be fairly good, although lack of effective treatment before the mid-1970s means information on long-term efficacy is limited.

Hyperchloremic acidosis is a form of metabolic acidosis associated with a normal anion gap, a decrease in plasma bicarbonate concentration, and an increase in plasma chloride concentration (see anion gap for a fuller explanation). Although plasma anion gap is normal, this condition is often associated with an "increased" urine anion gap, due to the kidney's inability to secrete ammonia.

Neutropenia is a manifestation of this disease. Granulocyte colony-stimulating factor (G-CSF, e.g. filgrastim) therapy can reduce the risk of infection.

Hyperprolinemia, also referred to as prolinemia or prolinuria, is a condition which occurs when the amino acid proline is not broken down properly by the enzymes proline oxidase or pyrroline-5-carboxylate dehydrogenase, causing a buildup of proline in the body.

The main causes of hypokalemic acidosis are systemic disorders that can be divided into:

- Carbonic anhydrase inhibitors such as acetazolamide

- Dialysis, in the post-treatment

- Diarrhea

- Renal tubular acidosis

- Treated DKA with insulin therapy

- VIPoma

Proximal renal tubular acidosis (pRTA) or Type 2 Renal tubular acidosis (RTA) is a type of RTA caused by a failure of the proximal tubular cells to reabsorb filtered bicarbonate from the urine, leading to urinary bicarbonate wasting and subsequent acidemia. The distal intercalated cells function normally, so the acidemia is less severe than dRTA and the urine can acidify to a pH of less than 5.3. pRTA also has several causes, and may occasionally be present as a solitary defect, but is usually associated with a more generalised dysfunction of the proximal tubular cells called Fanconi syndrome where there is also phosphaturia, glycosuria, aminoaciduria, uricosuria and tubular proteinuria.

Patients with type 2 RTA are also typically hypokalemic due to a combination of secondary hyperaldosteronism, and potassium urinary losses - though serum potassium levels may be falsely elevated because of acidosis. Administration of bicarbonate prior to potassium supplementation might lead to worsened hypokalemia, as potassium shifts intracellularly with alkanization.

The principal feature of Fanconi syndrome is bone demineralization (osteomalacia or rickets) due to phosphate and vitamin D wasting.

A 2005 study on rats suggested that hyperprolininemia causes cognitive dysfunction.

SUCLA2 and RRM2B related forms result in deformities to the brain. A 2007 study based on 12 cases from the Faroe Islands (where there is a relatively high incidence due to a founder effect) suggested that the outcome is often poor with early lethality. More recent studies (2015) with 50 people with SUCLA2 mutations, with range of 16 different mutations, show a high variability in outcomes with a number of people surviving into adulthood (median survival was 20 years. There is significant evidence (p = 0.020) that people with missense mutations have longer survival rates, which might mean that some of the resulting protein has some residual enzyme activity.

RRM2B mutations have been reported in 16 infants with severe encephalomyopathic MDS that is associated with early-onset (neonatal or infantile), multi-organ presentation, and mortality during infancy.

In the fetus, the normal range differs based on which umbilical vessel is sampled (umbilical vein pH is normally 7.25 to 7.45; umbilical artery pH is normally 7.20 to 7.38). In the fetus, the lungs are not used for ventilation. Instead, the placenta performs ventilatory functions (gas exchange). Fetal respiratory acidemia is defined as an umbilical vessel pH of less than 7.20 and an umbilical artery PCO of 66 or higher or umbilical vein PCO of 50 or higher.

Respiratory acidosis results from a build-up of carbon dioxide in the blood (hypercapnia) due to hypoventilation. It is most often caused by pulmonary problems, although head injuries, drugs (especially anaesthetics and sedatives), and brain tumors can cause this acidemia. Pneumothorax, emphysema, chronic bronchitis, asthma, severe pneumonia, and aspiration are among the most frequent causes. It can also occur as a compensatory response to chronic metabolic alkalosis.

One key to distinguish between respiratory and metabolic acidosis is that in respiratory acidosis, the CO is increased while the bicarbonate is either normal (uncompensated) or increased (compensated). Compensation occurs if respiratory acidosis is present, and a chronic phase is entered with partial buffering of the acidosis through renal bicarbonate retention.

However, in cases where chronic illnesses that compromise pulmonary function persist, such as late-stage emphysema and certain types of muscular dystrophy, compensatory mechanisms will be unable to reverse this acidotic condition. As metabolic bicarbonate production becomes exhausted, and extraneous bicarbonate infusion can no longer reverse the extreme buildup of carbon dioxide associated with uncompensated respiratory acidosis, mechanical ventilation will usually be applied.

The TK2 related myopathic form results in muscle weakness, rapidly progresses, leading to respiratory failure and death within a few years of onset. The most common cause of death is pulmonary infection. Only a few people have survived to late childhood and adolescence.