Fasting before physical and is "black coffee" really OK

#1: Post by **iploya** » July 15th, 2022, 9:26 am

I could just Google this but thought it would be more interesting to ask here.

I had my physical earlier this week. I fasted before. I am always told I can drink pure black coffee. What I had that morning was two double espressos. Does that count as "black coffee" or was this rule of thumb created back when a cup of stale, dilute Folgers was the reference point?

At least one of the espressos was a natural process coffee, which I understand has more natural sugars in the bean, but not sure if this is enough to register. Incidentally, my glucose was 106 (reference range 70-99).

#2: Post by **PIXIllate** » July 15th, 2022, 9:36 am

I'd say if your normal day includes the two espresso then I'd want that included in my baseline. Personally I'm physically addicted to caffeine and have significant side effects if I don't get my two shots in the morning.

#3: Post by **baldheadracing** » July 15th, 2022, 10:01 am

I'd say that it depends on the blood test/reasons for the test, e.g., checking for early signs of diabetes. For example, caffeine can indirectly affect blood sugar levels so coffee isn't recommended before some types of tests/reasons. I recently had to get some blood tests re-done because I had black coffee during the fasting period before the tests and the test results came back a little high.

#4: Post by **Graymatters** » July 15th, 2022, 10:05 am

I do some fasting/intermittent fasting, so I've looked in to acceptable beverages. Black coffee/espresso shouldn't make a difference for the vast majority of folks, but the only way for you to be sure would be to do a blood sugar test before and a half hour after the espresso.

#5: Post by **jdrobison** » July 15th, 2022, 11:17 am

I think that it really depends on your tests and what markers you're looking for.

Drinking a cup of coffee raises cortisol and testosterone levels, if I recall correctly. Drinking coffee regularly reduces insulin sensitivity but I think that studies have concluded that a cup of coffee doesn't elevate glucose. In other words, unless you abstain for a long time, your glucose is probably going to test the same whether you have a cup before blood tests or not, but your cortisol and testosterone might be affected.

#6: Post by **Nate42** » July 15th, 2022, 12:39 pm

Depends on the point of the test. Many doctors will tell you black coffee is fine for a fasting test, but they are assuming weak filter coffee. Espresso is high in triglycerides and I have seen it impact my blood tests so I recommend skipping it for those types of tests.

#7: Post by **chipman** » July 15th, 2022, 12:56 pm

I would ask my doctor. But, that's just me.

#8: Post by **BaristaBoy E61** » July 15th, 2022, 1:13 pm

Plain water is always fine. Follow your doctor's specific instructions.

BTW: DON'T have Cherry anything when prepping for a colonoscopy!

#9: Post by **TomC** » July 15th, 2022, 4:41 pm

Nate42 wrote:Depends on the point of the test. Many doctors will tell you black coffee is fine for a fasting test, but they are assuming weak filter coffee. Espresso is high in triglycerides and I have seen it impact my blood tests so I recommend skipping it for those types of tests.

There are many factors to consider in studies like this, but in most cases, the connection between coffee/espresso and its affects on triglycerides has been argued over for decades without very clear answers. The results also vary significantly depending on the health, age and weight of the subjects that were tested. But most of the meta analysis done from these trials conducted in Scandinavia were done using boiled coffee, not espresso, which likely doesn't contain the same level of Cafestol.

#10: Post by **Marcelnl** » July 15th, 2022, 7:15 pm

In addition to that, if you're drinking espresso on a daily basis that shot just prior to getting blood taken for testing is IMO unlikely to affect the outcome.

https://www.researchgate.net/publicatio ... erol_Level

Bloodsugar is just an indication, for longer term the HbA1c value is more informative.

https://www.mayoclinic.org/diseases-con ... 0be%20safe.