It appears to me at least, to be a subject that seems to need some clarification.

some eg’s;

https://www.healthline.com/health/food-nutrition/clear-liquid-diet

https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/clear-liquid-diet/art-20048505

https://www.adclinic.com/what-is-a-clear-liquid-diet/

OK is seems clear that a clear liquid should be something that can be seen through and hopefully still helps maintain some nutrient intake?

Why then in some instances is coffee considered both a clear liquid and not? eg: when fasting for blood tests or when preparing for colonostomy.

Of tisanes, in a medical examination perspective, are the various state altering chemicals relevant or irrelevant?

roughbarked said:

It appears to me at least, to be a subject that seems to need some clarification.

some eg’s;

https://www.healthline.com/health/food-nutrition/clear-liquid-diet

https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/clear-liquid-diet/art-20048505

https://www.adclinic.com/what-is-a-clear-liquid-diet/

OK is seems clear that a clear liquid should be something that can be seen through and hopefully still helps maintain some nutrient intake?

Why then in some instances is coffee considered both a clear liquid and not? eg: when fasting for blood tests or when preparing for colonostomy.

Of tisanes, in a medical examination perspective, are the various state altering chemicals relevant or irrelevant?

Is there a doctor in the house?

My guess as regards fasting is that all clear liquids other than water are banned in order not to affect baseline potassium or other factors that are affected by digestion. So sugar in coffee wouldn’t be good.

mollwollfumble said:

My guess as regards fasting is that all clear liquids other than water are banned in order not to affect baseline potassium or other factors that are affected by digestion. So sugar in coffee wouldn’t be good.

Chicken soup?

Ones own urine is a clear liquid I asked the doctor this and he agreed

Zarkov said:

Ones own urine is a clear liquid I asked the doctor this and he agreed

There are precautions that need to be taken if you do this.
Avoid the first and last urine as it’s likely to contain bacteria.
And put a clothes peg on your nose.

Am I right in thinking that a clear liquid diet is only for people who are about to undergo a colonoscopy? That’s what the Mayo clinic implies.

mollwollfumble said:

Am I right in thinking that a clear liquid diet is only for people who are about to undergo a colonoscopy? That’s what the Mayo clinic implies.

There are other reasons for clear liquid diets but I would always query things like chicken soup because it isn’t very clear and it is full of fats and stuff.
I’d query milkless and sugarless coffee because it is hardly clear and clearly contains sediments.