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Doctor insights on: Can I Have Coffee Before A Fasting Blood Test

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Dr. Terri Washington
Board Certified, Endocrinology
11 years in practice
927K people helped
1

1
Will drinking decaf black coffee before fasting blood test alter the results?

Dr. Terri Washington
Board Certified, Endocrinology
11 years in practice
927K people helped
Will drinking decaf black coffee before fasting blood test alter the results?

Yes: Could depending on the test, if is blood sugar or chol then coffee could make an impact. ...Read more

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Dr. Jack Hinkle
Board Certified
383K people helped
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Dr. Jeff McFadden
Board Certified, Family Medicine
19 years in practice
444K people helped
2

2
Could just a coffee 40 mins before blood test for ESR and C reactive protein influence the results? Need to do these tests today bur forget fasting.

Dr. Jeff McFadden
Board Certified, Family Medicine
19 years in practice
444K people helped
Could just a coffee 40 mins before blood test for ESR and C reactive protein influence the results? Need to do these tests today bur forget fasting.

Don't think so: Caffeine should not affect these results. Besides these are not acute phase reactant tests and take longer to change. ...Read more

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Dr. Jack Hinkle
Board Certified
383K people helped
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Dr. Jack Hinkle
Board Certified
383K people helped
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Dr. Orrin Ailloni-Charas
Board Certified, Anesthesiology
24 years in practice
1M people helped
3

3
Three cups of black coffee before my fasting blood test. Potassium came in at 5.7. Could this be the cause. I'm healthy otherwise.

Dr. Orrin Ailloni-Charas
Board Certified, Anesthesiology
24 years in practice
1M people helped
Three cups of black coffee before my fasting blood test. Potassium came in at 5.7. Could this be the cause. I'm healthy otherwise.

No. : Have the test repeated. Blood cells can break down and release potassium. If the specimen was drawn in a way that traumatized the red blood cells, or if it sat around a long time before being tested, it will have an artificially high potassium. ...Read more

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Dr. Robert Killian
Board Certified, General Practice
23 years in practice
327M people helped
4

4
Is it ok to drink black coffee when your fasting for blood test?

Dr. Robert Killian
Board Certified, General Practice
23 years in practice
327M people helped

Fasting for Labs: Yes. There are no sugar or fat calories in black coffee. ...Read more

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Dr. Jack Hinkle
Board Certified
383K people helped
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Dr. Milton Mintz
Board Certified, Geriatrics
62 years in practice
2M people helped
5

5
I have to fast for 12 hours before blood test. Can i drink black coffee during those 12 hours?

Dr. Milton Mintz
Board Certified, Geriatrics
62 years in practice
2M people helped

Yes: One cup won't change your results.

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Dr. Anne Larson
Board Certified, Hepatology
29 years in practice
378K people helped
6

6
Can drink coffee before blood test cause elevated alt?

Dr. Anne Larson
Board Certified, Hepatology
29 years in practice
378K people helped

No: In fact, coffee has been shown to lower ast and alt. ...Read more

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Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
7

7
Is it possible for me to drink coffee before a thyroid blood test?

Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped

You may: If thyroid blood test is the only test you are having, coffee is not likely to materially affect the results. Generally it is better to be fasting for lab tests. ...Read more

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Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
8

8
I drank a cup of coffee with cream and artificial sweetener before a blood test for diabetes, will this show up as diabetes?

Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
I drank a cup of coffee with cream and artificial sweetener before a blood test for diabetes, will this show up as diabetes?

Fasting: It is imperative to be fasting for at least 9 hours, preferably 12 hours before the test. ...Read more

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Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
9

9
I am 18 i woke up and drank coffee with 2 teaspoons of sugar and i took a blood test and the result was 108 is it normal ?

Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
I am 18 i woke up and drank coffee with 2 teaspoons of sugar and i took a blood test and the result was 108 is it normal ?

Depends: Blood glucose is best monitored in fasting condition. You should have fasted at least 8 hours not taken anything other than water. This result is not interpretable due to your intake of coffee and sugar before the blood draw. ...Read more

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Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
10

10
Can coffee give cause cancer do I need to have a blood test.

Dr. Gurmukh Singh
Board Certified, Pathology
44 years in practice
96M people helped
Can coffee give cause cancer do I need to have a blood test.

No and No: Coffee does not give you cancer and you do not need a blood test. Incidentally there is no good blood test for cancer. ...Read more

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Dr. Jack Hinkle
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