Interpreting Patient Labs/Charts

Sodium is the predominant cation of the ECF
Increase in [Na] = impaired Na excretion or dehydration
decrease in [Na] = overhydration, abnormal sodium losses, or sodium starvation.

  • Treat with water restriction
  • Na is a reliable indicator of a patient’s fluid status (changes in Na most often represent water imbalances and not salt imbalances)

Carbon dioxide content = [HCO3] + [CO2]
Chloride = major inorganic anion in ECF

  • Decreased chloride = metabolic alkalosis
  • Increased chloride = hyperchloremic metabolic acidosis

Phosphate is the major determinant of intracellular concentration

  • Causes of hyperphosphatemia:  kidney problems, low PTH
  • Causes of hypophsophatemia:  malnourishment, high amounts of Al-containing antacids, alcoholics, sepsis
  • Phosphate concentrations increase with renal dysfunction
  • Decrease with excess aluminum antacids

Glucose should be measured in both the fasting and postprandial state
BUN (blood urea nitrogen) is the end-product of protein metabolism

  • BUN reflects renal function because the urea nitrogen in blood is filtered completely through the glomerulus of the kidney then reabsorbed and tubularly secreted within the nephrons
  • An increase in BUN is most commonly caused by Acute/chronic renal failure
    • Measuring BUN can tell you renal dysfunction (but not necessarily to what extent)


  • Rate of formation is constant and determined by muscle mass.
  • Excreted renally via glomerular filtration.  Thus as glomerular filtration rate decreases, serum creatinine (Scr) will increase proportionately
  • Difficult to obtain an accurate creatinine clearance value clinically

Complete Blood Count (CBC) = total WBCs + hemoglobin + hematocrit + platelets
WBCs (neutrophils, lymphocytes, monocytes, eosinophils, basophils)

  • Neutrophils:  A “left shift” indicates an increase
    • Ex. During bacterial infections

Hemoglobin (Hgb) determines the oxygen transport capability of the blood

  • Causes of Decreases in hematocrit = bleeding, anemias, bone marrow suppressant effects, hemolysis
  • Causes of increases in hematocrit = hemoconcentration, chronic hypoxia


  • Renal failure can cause hypermagnesemia


  • Increased with renal dysfunction, acidosis, burns, injuries
  • Decreased with alkalosis, diuretics, v/d

Red Blood Cells

  • Transport oxygen
  • Concentration detects anemia

The following two diagrams are commonly filled in lab values (but are typically not explicitly labeled as shown below):

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