Diabetes mellitus type 1 laboratory findings

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Case #1

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Patient Information Type 1 Type 2
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Laboratory Findings

Laboratory findings in type 1 diabetes based on presentation
		Classic new onset	Diabetic Ketoacidosis
Blood	Glucose	Random:  random (nonfasting) plasma glucose concentration of 200 mg/dL or higher Fasting plasma glucose concentration of 126 mg/dL (6.99 mmol/L) or higher	Random glucose sugar is more then 250 mg/dl
	HbA1c	HbA1c level of 6.5% or higher	Not applicable
	C-Peptide below	below 5 µU/mL	Not applicable
	Islet-cell (IA2)	Measurements of IA2 autoantibodies within 6 months of diagnosis can help differentiate between type 1 and type 2 DM	Not applicable
	Anti-GAD65	Usually present	Not applicable
	Anti-insulin autoantibodies	Usually present	Not applicable
	CBC with differential	Normal	Mildly elevated with normal differential
	Basic metabolic panel	Normal	Serum bicarbonate < 18 mEq/L Serum Sodium: Often normal or elevated Serum Phosphate: Often normal or elevated Serum Potassium: Often normal or elevated
	Serum Creatinine	Normal	Often elevated
	Serum calicum	Normal	Decreased
	Serum amylase	Normal	Mildly elevated
	Serum Lipase	Normal	Normal
	Serum osmorality	Normal	Normal
	Serum Ketones	Normal	High
	Anion gap	normal	High
	Arterial Blood gas	Normal	Metabolic acidosis, compensated by respiratory alkalosis
Urine	Glucose	May or may not be present(Blood glucose should be more then 200 mg/dl to appear in urine)	Often present
	Ketones	absent	Present

There are two different tests your doctor can use to determine whether you have pre-diabetes or diabetes: the fasting plasma glucose test (FPG) or the oral glucose tolerance test (OGTT). The blood glucose levels measured after these tests determine whether you have a normal metabolism, or whether you have pre-diabetes or diabetes. If your blood glucose level is abnormal following the FPG, you have impaired fasting glucose (IFG); if your blood glucose level is abnormal following the OGTT, you have impaired glucose tolerance (IGT).

                                           
                                           FPG                          OGTT

The most useful laboratory test to distinguish Type 1 from Type 2 diabetes is the C-peptide assay, which is a measure of endogenous insulin production since external insulin (to date) has included no C-peptide. However, C-peptide is not absent in Type 1 diabetes until insulin production has fully ceased, which may take months. The presence of anti-islet antibodies (to Glutamic Acid Decarboxylase, Insulinoma Associated Peptide-2 or insulin), or lack of insulin resistance, determined by a glucose tolerance test, would also be suggestive of Type 1. As opposed to that, many Type 2 diabetics still produce some insulin internally, and all have some degree of insulin resistance.

Testing for GAD 65 antibodies has been proposed as an improved test for differentiating between Type 1 and Type 2 diabetes.