Felis ISSN 2398-2950

Blood biochemistry: glucose

Contributor(s): Kathleen P Freeman


  • Physiological plasma levels of glucose are maintained by glucagon (raises glucose) and insulin (lowers glucose) to ensure that a continuous supply of glucose is available as an energy source for cell metabolism.
  • Absorbed via the small intestine, glucose is stored as glycogen in liver and muscle and liberated when plasma levels fall.
  • Other hormones can raise plasma glucose by increasing gluconeogenesis or glycogenolysis or increasing/decreasing utilization.
  • Any condition which affects these hormones will influence plasma glucose levels.
  • Hypoinsulinism (diabetes mellitus Diabetes mellitus)   →   hyperglycemia.
  • Cortisol, adrenaline, growth hormone, progesterone, xylazine   →   increase glucose levels.


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  • Dextrostix used with whole blood only; gives a semiquantitative indicator of gross changes in plasma glucose.

Specific assays

  • 3 glucose specific enzyme methods commonly in use:
    • Glucose oxidase (GO).
    • Herokinase (HK).
    • Glucose dehydrogenase (GD).
  • Glucose oxidase reaction - results said to approach true glucose value under reliable laboratory conditions (used in glucose specific urine test strips).
  • Ortho-toluidine - also measures galactose and mannose, but these are considered insignificant; simple, fast test.

Non-specific assays

  • Nelson-Somogyi and Folin-Wu - may give slightly higher than true levels, the former more specific than the latter.
  • Ferricyanide - approaches true glucose level.


  • Widely available.

Technique (intrinsic) limitations

  • Some laboratory methods affected by presence of enzyme inhibitors/activators.
  • Glycolysis by erythrocytes estimated to reduce glucose concentration by approximately 10% per hour at room temperature.
  • Prompt separation of serum/plasma from cells, and refrigeration, will reduce glycolysis.

Result Data

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Further Reading


Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Martin G J W et al (1999) Food intake and blood glucose in normal and diabetic cats fed ad libitum. J Fel Med Surg 1(4), 241-251.
  • Steiner J M & Bruyette D S (1996) Canine Insuloma. Comp Cont Educ Prac Vet 18(1), 13-24.
  • Plotnick A N (1995) Diagnosis of diabetes mellitus in dogs and cats, contrasts and comparisons. Vet Clin North Am Small Anim Pract 25(3), 563-570.

Other sources of information

  • Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine.5th edn. Philadelphia: W B Saunders & Co.
  • Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
  • Feldman E C & Nelson R W (1996) Canine and Feline Endocrinology. 2nd edn. Philadelphia: W B Saunders & Co.
  • Bonagura J D & Kirk R W (eds) (1995) Kirk's Current Veterinary Therapy XII. Small Animal Practice. Philadelphia.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.