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Q. Can I drink coffee (without the cream and sugar) before a fasting blood test?

A. Not if you want accurate results. Don’t have coffee, tea, juice or any liquid other than water. Don’t chew gum, don’t smoke, don’t even exercise. Be a monk until the test is done.

The fasting blood test, also known as a fasting blood sugar (FBS) or blood sugar level test, measures the amount of glucose in the bloodstream. It’s used primarily to screen for diabetes and to monitor hyperglycemia (too much glucose) or hypoglycemia (not enough glucose).

Caffeine, which is absorbed into the system at an incredible rate, can temporarily raise blood sugar levels and make for an inaccurate FBS reading. Moreover, the chemical composition of roasted coffee beans is nearly 40 percent sugar (in the form of polysaccharides). Drinking coffee will stimulate the pancreas to excrete insulin, which balances blood sugar, and throw off your test results.