Although blood gas sampling is not always essential for the diagnosis of acidosis, a low pH (in either a venous or arterial sample) does support the diagnosis. If the pH is low (under 7.35) and the bicarbonate levels are decreased (<24 mmol/L), metabolic acidemia is present, and metabolic acidosis is presumed. If the patient has other coexisting acid-base disorders, the pH may be low, normal or high in the setting of metabolic acidosis. If a setting of a cause for metabolic acidosis being noted in the patient's history, a low serum bicarbonate indicates metabolic acidosis even without measurement of serum pH.

Other tests relevant in this context are electrolytes (including chloride), glucose, renal function, and a full blood count. Urinalysis can reveal acidity (salicylate poisoning) or alkalinity (renal tubular acidosis type I). In addition, it can show ketones in ketoacidosis.

To distinguish between the main types of metabolic acidosis, a clinical tool called the anion gap is considered very useful. It is calculated by subtracting the sum of the chloride and bicarbonate levels from the sum of the sodium and potassium levels.

As sodium is the main extracellular cation, and chloride and bicarbonate are the main anions, the result should reflect the remaining anions. Normally, this concentration is about 8-16 mmol/L (12±4). An elevated anion gap (i.e. > 16 mmol/L) can indicate particular types of metabolic acidosis, particularly certain poisons, lactate acidosis, and ketoacidosis.

As the differential diagnosis is made, certain other tests may be necessary, including toxicological screening and imaging of the kidneys. It is also important to differentiate between acidosis-induced hyperventilation and asthma; otherwise, treatment could lead to inappropriate bronchodilation.

A pH under 7.1 is an emergency, due to the risk of cardiac arrhythmias, and may warrant treatment with intravenous bicarbonate. Bicarbonate is given at 50-100 mmol at a time under scrupulous monitoring of the arterial blood gas readings. This intervention, however, has some serious complications in lactic acidosis, and in those cases, should be used with great care.

If the acidosis is particularly severe and/or intoxication may be present, consultation with the nephrology team is considered useful, as dialysis may clear both the intoxication and the acidosis.

Several different problems may lead to the diagnosis, usually by two years of age:

- seizures or other manifestations of severe fasting hypoglycemia

- hepatomegaly with abdominal protuberance

- hyperventilation and apparent respiratory distress due to metabolic acidosis

- episodes of vomiting due to metabolic acidosis, often precipitated by minor illness and accompanied by hypoglycemia

Once the diagnosis is suspected, the multiplicity of clinical and laboratory features usually makes a strong circumstantial case. If hepatomegaly, fasting hypoglycemia, and poor growth are accompanied by lactic acidosis, hyperuricemia, hypertriglyceridemia, and enlarged kidneys by ultrasound, gsd I is the most likely diagnosis. The differential diagnosis list includes glycogenoses types III and VI, fructose 1,6-bisphosphatase deficiency, and a few other conditions (page 5), but none are likely to produce all of the features of GSD I.

The next step is usually a carefully monitored fast. Hypoglycemia often occurs within six hours. A critical blood specimen obtained at the time of hypoglycemia typically reveals a mild metabolic acidosis, high free fatty acids and beta-hydroxybutyrate, very low insulin levels, and high levels of glucagon, cortisol, and growth hormone. Administration of intramuscular or intravenous glucagon (0.25 to 1 mg, depending on age) or epinephrine produces little rise of blood sugar.

The diagnosis is definitively confirmed by liver biopsy with electron microscopy and assay of glucose-6-phosphatase activity in the tissue and/or specific gene testing, available in recent years.

Treatment of uncompensated metabolic acidosis is focused upon correcting the underlying problem. When metabolic acidosis is severe and can no longer be compensated for adequately by the lungs, neutralizing the acidosis with infusions of bicarbonate may be required.

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.

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.

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:

The underlying cause determines the prognosis of lactic acidosis. In sepsis, elevated lactate levels correlate with mortality. The mortality of lactic acidosis in people taking metformin was previously reported to be 50%, but in more recent reports this was closer to 25%.

Serum glucose levels are measured to document the degree of hypoglycemia. Serum electrolytes calculate the anion gap to determine presence of metabolic acidosis; typically, patients with glycogen-storage disease type 0 (GSD-0) have an anion gap in the reference range and no acidosis. See the Anion Gap calculator.

Serum lipids (including triglyceride and total cholesterol) may be measured. In patients with glycogen-storage disease type 0, hyperlipidemia is absent or mild and proportional to the degree of fasting.

Urine (first voided specimen with dipstick test for ketones and reducing substances) may be analyzed. In patients with glycogen-storage disease type 0, urine ketones findings are positive, and urine-reducing substance findings are negative. However, urine-reducing substance findings are positive (fructosuria) in those with fructose 1-phosphate aldolase deficiency (fructose intolerance).

Serum lactate is in reference ranges in fasting patients with glycogen-storage disease type 0.

Liver function studies provide evidence of mild hepatocellular damage in patients with mild elevations of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels.Plasma amino-acid analysis shows plasma alanine levels as in reference ranges during a fast.

Evaluation of a patient with suspected glycogen-storage disease type 0 requires monitored assessment of fasting adaptation in an inpatient setting.

Patients typically have hypoglycemia and ketosis, with lactate and alanine levels in the low or normal part of the reference range approximately 5–7 hours after fasting.

A glucagon tolerance test may be needed if the fast fails to elicit the expected rise in plasma glucose. Lactate and alanine levels are in the reference range.

By contrast, a glucagon challenge test after a meal causes hyperglycemia, with increased levels of plasma lactate and alanine.

Oral loading of glucose, galactose, or fructose results in a marked rise in blood lactate levels.

Preventing recurrence of hyperkalemia typically involves reduction of dietary potassium, removal of an offending medication, and/or the addition of a diuretic (such as furosemide or hydrochlorothiazide). Sodium polystyrene sulfonate and sorbitol (combined as Kayexalate) are occasionally used on an ongoing basis to maintain lower serum levels of potassium though the safety of long-term use of sodium polystyrene sulfonate for this purpose is not well understood.

High dietary sources include vegetables such as avocados, tomatoes and potatoes, fruits such as bananas, oranges and nuts.

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.

A genetic test is available for Type 1 PSSM. This test requires a blood or hair sample, and is less-invasive than muscle biopsy. However, it may be less useful for breeds that are more commonly affected by Type 2 PSSM, such as light horse breeds. Often a muscle biopsy is recommended for horses displaying clinical signs of PSSM but who have negative results for GYS1 mutation.

A muscle biopsy may be taken from the semimembranosis or semitendinosis (hamstring) muscles. The biopsy is stained for glycogen, and the intensity of stain uptake in the muscle, as well as the presence of any inclusions, helps to determine the diagnosis of PSSM. This test is the only method for diagnosing Type 2 PSSM. Horses with Type 1 PSSM will usually have between 1.5-2 times the normal levels of glycogen in their skeletal muscle. While abnormalities indicating muscle damage can be seen on histologic sections of muscle as young as 1 month of age, abnormal polysaccharide accumulation may take up to 3 years to develop.

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.

Normal serum potassium levels are generally considered to be between 3.5 and 5.3 mmol/L. Levels above 5.5 mmol/L generally indicate hyperkalemia, and those below 3.5 mmol/L indicate hypokalemia.

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)

Horses with PSSM have elevated levels of muscle glycogen at rest. During exercise, glycogen levels are depleted faster than is seen in unaffected horses, and are reduced down to levels considered normal for a resting non-PSSM horse. This demonstrates that glycogen metabolism is actually normal in these animals. However, PSSM horses synthesize muscle glycogen at double the rate of a normal horse once exercise has ceased, which leads to elevated muscle glycogen. The exact mechanism of abnormal glucose metabolism has not yet been established, but it may have similarities to phosphofructokinase deficiency in humans.

Quarter Horse-related breeds with PSSM show insulin sensitivity, which improves glucose uptake by cells, and these horses clear the blood of glucose more quickly after eating than unaffected horses. This provides easy access to glucose by the muscles, which can then use the substrate to produce glycogen. The GYS1 defect, which up-regulates the glycogen synthase enzyme, allows the muscles to use this glucose to rapidly produce glycogen for storage in the muscle. Surprisingly, increased insulin sensitivity is not seen in draft horse breeds.

Dietary and exercise manipulation may be used to counteract these metabolic changes. Approximately 50% of horses that adhere to the dietary recommendations, and 90% of horses that adhere to both dietary and exercise recommendations, have few to no episodes of exertional rhabdomyolysis.

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

Diagnosis can be made by checking fasting and post prandial insulin levels either with normal meal or with 100gms of oral glucose

Hypokalemic acidosis is a normal anion gap metabolic acidosis that has various direct and associated symptoms. Symptoms are associated with hypokalemia instead of hyperkalemia.

Treatment consists of oral bicarbonate supplementation. However, this will increase urinary bicarbonate wasting and may well promote a bicarbonate . The amount of bicarbonate given may have to be very large to stay ahead of the urinary losses. Correction with oral bicarbonate may exacerbate urinary potassium losses and precipitate hypokalemia. As with dRTA, reversal of the chronic acidosis should reverse bone demineralization.

Thiazide diuretics can also be used as treatment by making use of contraction alkalosis caused by them.

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.

The differential diagnosis of normal anion gap acidosis is relatively short (when compared to the differential diagnosis of "acidosis"):

- Hyperalimentation

- Acetazolamide and other carbonic anhydrase inhibitors

- Renal tubular acidosis

- Diarrhea: due to a loss of bicarbonate. This is compensated by an increase in chloride concentration, thus leading to a normal anion gap, or hyperchloremic, metabolic acidosis. The pathophysiology of increased chloride concentration is the following: fluid secreted into the gut lumen contains higher amounts of Na than Cl; large losses of these fluids, particularly if volume is replaced with fluids containing equal amounts of Na and Cl, results in a decrease in the plasma Na concentration relative to the Clconcentration. This scenario can be avoided if formulations such as lactated Ringer’s solution are used instead of normal saline to replace GI losses.

- Ureteroenteric fistula - an abnormal connection (fistula) between a ureter and the gastrointestinal tract

- Pancreaticoduodenal fistula - an abnormal connection between the pancreas and duodenum

- Spironolactone

As opposed to high anion gap acidosis (which involves increased organic acid production), normal anion gap acidosis involves either increased production of chloride (hyperchloremic acidosis) or increased excretion of bicarbonate.

Treatment is typically achieved via diet and exercise, although metformin may be used to reduce insulin levels in some patients (typically where obesity is present). A referral to a dietician is beneficial. Another method used to lower excessively high insulin levels is cinnamon as was demonstrated when supplemented in clinical human trials.

A low carbohydrate diet is particularly effective in reducing hyperinsulinism.

A healthy diet that is low in simple sugars and processed carbohydrates, and high in fiber, and vegetable protein is often recommended. This includes replacing white bread with whole-grain bread, reducing intake of foods composed primarily of starch such as potatoes, and increasing intake of legumes and green vegetables, particularly soy.

Regular monitoring of weight, blood sugar, and insulin are advised, as hyperinsulinemia may develop into diabetes mellitus type 2.

It has been shown in many studies that physical exercise improves insulin sensitivity. The mechanism of exercise on improving insulin sensitivity is not well understood however it is thought that exercise causes the glucose receptor GLUT4 to translocate to the membrane. As more GLUT4 receptors are present on the membrane more glucose is taken up into cells decreasing blood glucose levels which then causes decreased insulin secretion and some alleviation of hyperinsulinemia. Another proposed mechanism of improved insulin sensitivity by exercise is through AMPK activity. The beneficial effect of exercise on hyperinsulinemia was shown in a study by Solomon et al. (2009), where they found that improving fitness through exercise significantly decreases blood insulin concentrations.

Increased levels predispose for gout and, if very high, kidney failure. The metabolic syndrome often presents with hyperuricemia. Prognosis is good with regular consumption of Allopurinol.

People with gout, and by inference hyperuricemia, are significantly less likely to develop Parkinson's disease, unless they also require diuretics.