Blood biochemistry: serial blood glucose

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• Serial blood glucose measurement gives much better assessment of pattern of glycemic control than a 'spot' sample.
• Allows confirmation of time of peak insulin activity and duration of insulin effect.
• Ideally sample at 1-2 hourly intervals.

• Diabetic cases: assess insulin responsiveness, peak activity, duration and extent of glycemic control over 24 hour period.
• Stabilization of diabetic cases .
• Best used early in therapy to allow optimization of feeding and insulin administration.

• Very helpful where glycemic control deteriorating.

• Islet cell tumor (insulinoma) - very rare.

• Test of choice for identification of the 'Somogyi phenomenon' (insulin-induced hypoglycemia inducing a rebound hyperglycemia).

• Jugular or regional (cephalic, saphenous) vein .

• 0.5 ml whole blood each sample (or a drop of blood if glucometer available).

Step 1

• Fast animal for 12 hours prior to testing.
• Initial blood into fluoride oxalate (0.5 ml) labeling sample with time and owner's name. 
   Consider in-dwelling intravenous catheter to reduce stress of sampling. Flush with heparinized saline and cap in normal manner.

Step 2

• Take further samples into fluoride oxalate at 1-2 hourly intervals for up to 24 hours if required.
   Diabetic management and feeding regimes should be as normal as possible for the individual.
   Results markedly affected by stress at sampling, inappetence and exercise.

• Label sequential samples with care. Easy to mix up.

• Store samples in refrigerator prior to dispatch.

• Standard submission to laboratory.
• Package according to mailing regulations .

• Glucose assay widely available.

• Requires 12-24 hour hospitalization of patient.

• Shortened tests which are run over normal working day can miss significant hyperglycemia overnight.
• A 2-3 hour post-prandial sample can be taken after evening meal.

• Diabetes mellitus:
  • Persistent hyperglycemia inadequate insulin dose/insulin antagonism.
  • Initial rapid hypoglycemia followed by compensatory hyperglycemia (Somogyi overswing) insulin overdose.
  • Initial stabilization of glucose levels then evening hyperglycemia inadequate duration of insulin action.
• Islet cell tumor (rare in cat): persistent hypoglycemia.

• 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.

• Dr David Bruyette DVM DipACVIM, VCA West Los Angeles, 1818 South Sepulveda Boulevard, Los Angeles, CA 90025, USA.

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