​Symptoms and Signs – Differential Diagnosis of Acidosis 
Normal anion gap
Reduced  HCO3 GI loss: diarrhoea, fistula (biliary, intestinal, pancreatic), ileostomy,
ureterosigmoidostomy
Renal loss: renal tubular acidosis (type 2), renal tubular damage (e.g. drugs/
heavy metals), hyperparathyroidism, acetazolamide
Inceased H+ Renal tubular acidosis (1 & 4), ammonium chloride ingestion)

High anion gap
Ketoacidosis: diabetes mellitus, excess alcohol, starvation
Lactic acidosis:
Tissue hypoxia, e.g. shock (haemorrhagidseptic), severe exercise, severe
anaemia
Drugs: metformin, ethanol, methanol, ethylene glycol, zidovudine
D-Lactic acidosis (short gut syndrome)
Leukaemia
Lymphoma
Liver failure
Glucose-6-phosphatase deficiency, mitochondrial disorders (e.g. MELAS)
Renal failure
Salicylate poisoning

Respiratory
CNS
Organic disease involving respiratory centre (e.g. vascular, infection,
inflammation, trauma, tumour)
Drugs: opiates, benzodiazepines, barbiturates and other anaesthetic agents

Lungs
Severe asthma (uncommonly), COPD, large airway obstruction, obstructive sleep apnoea



Neuromuscular
Motor neurones: Guillain-Barre syndrome, motor neurone disease, poliomyelitis, acute porphyria

Neuromuscular junction/muscle: myasthenia gravis, muscular dystrophies, muscle
relaxants, diaphagmatic paralysis

Chest wall
Severe kyphoscoliosis, severe obesity, traumatic 'flail chest'