Serum and Fluoride Oxalate tubes (serum only required if fresh)
This test examines the rise in levels of insulin following administration of glucose in the form of a syrup. Samples are taken immediately before feeding the syrup, to assess basal levels of glucose and insulin, and at 60 and 90 minus post-administration.
Note: if glucose is being measured and it is possible to deliver fresh samples, then serum is preferred over fluoride oxalate tubes. This is because the sodium fluoride in these tubes lyses red blood cells and will reduce the true glucose concentration by between 7 and 12%. However, prompt delivery of serum samples for glucose is normally only possible with in-patients physically located at the practice at the time of sampling. For all other samples, a fluoride oxalate tube will produce the most reliable glucose result.