Lifescan OneTouch Ultra Owner's Booklet page 42

While at the lab:
◗
Make sure that the meter test and the lab test are performed within
15 minutes of each other.
◗
Wash your hands before obtaining a blood sample.
◗
Use only fresh capillary blood obtained from the fingertip.
You may still have a variation from the result because blood glucose
levels can change significantly over short periods, especially if you have
recently eaten, exercised, taken medication, or experienced stress.
In addition, if you have eaten recently, the blood glucose level from
a fingerstick can be up to 70 mg/dL higher than blood drawn from a
vein (venous sample) used for a lab test.
for eight hours before doing comparison tests. Factors such as the
amount of red blood cells in the blood (a high or low hematocrit) or
the loss of body fluid (severe dehydration) may also cause a meter result
to be different from a laboratory result.
References
1. Surwit, R.S., and Feinglos, M.N.: Diabetes Forecast (1988), April, 49–51.
2. Sacks, D.B.: "Carbohydrates." Burtis, C.A., and Ashwood, E.R. (ed.), Tietz Textbook
of Clinical Chemistry. Philadelphia: W.B. Saunders Company (1994), 959.
2 Therefore, it is best to fast
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