How many hour fasting do you do

I have an doctor visit tomorrow morning. I normally just skip breakfast get my blood drawn and eat after.

But this time they told me to fast 18 hours. That’s a long time.
It’s going to end up being 14 or 15 which is going to have to be enough.

It used to be that 8 hours was considered fasting.
I try to be consistent so my blood work has some consistency, but maybe I need to rethink my usual 12 hours or so.

I do 12-14 hours fasting for bloodwork. I know that’s longer than the standard recommendation but I don’t find it difficult to comply with.

In fact, it was blood work and medical procedure fasting that showed me the beneficial effect it has on blood sugar levels. Whenever I fast, providing my basal rates are close, my glucose average drops and the variability goes down significantly.

I suspect that your 14-15 hour fast will be good enough. Did the doctor tell you why s/he wanted that specific length fast? Will you drink coffee before the blood draw?

I will not drink coffee, because I don’t want to cause a spike in sugar.
It does that to me moderately.
I can hold off. Really I ate dinner at 6. And my appointment is at 8. I figure I’ll get my blood drawn after that and then I’ll get coffee.
It’s not that difficult really, I’ve just never been told this 18 hour fasting thing.

My fasting story is not related to a blood draw, but a knee surgery I had in 2010 (severely torn meniscus with a floater piece). My surgery was at 1:00 PM and they required me to fast after dinner, which I believe was around 6:30 PM, but the kicker was no fluids either because of the anesthesia. All I could do was brush my teeth and rinse whenever the dry mouth got unbearable.

Long story short, by the time they tried to find a vein during pre-op, I was so dehydrated that the nurse kept switching arms, even got frustrated over the struggle. After they were finally successful (took probably 5 - 6 times, but felt like 25) I asked why they made me stop fluids after dinner with my afternoon surgery time. The nurse said that they always require that! So I asked about if my surgery would have been at 8 :00 AM, would I still stop fluids right after dinner. They replied, Yes, of course, we want at least 12 hours without food and fluids to lessen the chance of vomiting due to the anesthesia.

No reasoning with the nurse after my surgery about the vast difference in morning and afternoon surgery start times leading to increased dehydration could be understood. You would think at the least the “Where Waldo” search for a usable vein would have caused an AHA! moment, but unfortunately, it never seemed to.

To this day I have never been so thirsty and miserable in my life. Now, years later, I never go anywhere (whether on work days or the weekend) without my large water bottle in tow, no matter the season or temperature!


Fasting: great topic.
I’ve learned that eating is a pretty important habit, that we seem to mistakenly over exercise every 4 to 8 hrs!
My lifelong MDI approach was always based on a perspective of: “WHERE will I be at WHAT time, and when I get there, HOW EARLY or LATE will I be for my next feeding? Grrrrrr!. I HAVE to EAT!”.
Pump therapy, and a recent discussion with a promoter of short-term fasting, changed that broken mindset.
The promoter fasted 20+4: 20hrs fasting, + “4 hour window” to eat. It does not mean that they would eat for 4hrs straight; they have a 4hr window in their schedule, if they’d like to eat. Their fasting cycle was 9pm to 5pm (20hrs); + 4hr window (5pm to 9pm) for regular dinner time, and into bed by 10:30pm to start the day for tomorrow. No pre-bed snack, no breakfast, or lunch. Note: the promoter was not diabetic.

I started with 12hrs FASTING, and found how accurate my basal rates are, with some minor adjustments. I have since then fasted an entire 22hrs. The other benefit was change of mindset, “Oh! It’s noon already, I’ve GOT TO EAT!!”. No, you don’t!
You can easily do the required 18hrs. Drink lots of water, tea.

I have switched to 2 meals a day. And my control is better for sure.
While fasting my sugar is super flat.
The only time I am out of range is when I miscalculate carbs for my 2 meals.
Or if my sit has gone bad.
So I normally fast12 hours a day. Sometimes more.
I would try one meal a day, but I’m a little tentative about it

Eating is such a social event. Family and co workers.

Most people eat 3 meals. And even more.
I purposely do not eat after dinner, where the rest of my family eats a lot after dinner

My daughter skips breakfast because she isn’t hungry. So we have similar fasting just different times.

It was so drilled into me to eat 3 times a day it’s hard to break the habit


We inadvertently do IF. There’s farm chores to do in the morning. Since we only eat real, made from scratch food, grabbing something quick and easy isn’t really an option. It winds up being 10-11 am before I get breakfast made. I don’t really want any lunch after such a late breakfast. Dinner is usually around 4-5 pm, except for planting season when we don’t eat until after dark. So 11 months out of the year we do 18/6ish.

A lot of the time I don’t eat breakfast until after a doctor’s appointment, but again, it’s inadvertent. I just get anxious about doctors and don’t have an appetite. Oddly enough, though, I’ve never once been asked to fast for bloodwork. I wonder what I’m missing.

I probably wouldn’t eat breakfast at all most days if I wasn’t already cooking for my ravenous partner. I wake up hungry, but my morning coffee squelches that, so I couldn’t care less about breakfast after that.

I tell the doctor that if I have to fast, I am not doing the test. I only fast for surgery or when my wife demands it. One of the many advantages of being an old fart. Look forward to that day my friends.


Just getting my A1C done, I don’t need to fast. But most times I am as I also am not a big breakfast person, although I love a big breakfast!
Doing all the clinical trials and all the lab work that they have, I am usually asked for 9 hours fasting. And surgery, I have never run into a problem because the scheduler is told up from I have diabetes and it needs to be as early as possible. So most times that comes out to around 10-12 hours. I haven’t had any lab work done that asked for 18 hours. I wonder why so long.

Always eat if it’s just a blood test. Most fasting tests on routine labs will tell the provider your fasting blood sugar (fairly useless unless you confirm it’s a pattern/trend to be low or high around that time) and an accurate triglyceride count. 90% of the rest of it does not matter your fasting status.

My doc tell me he’d rather have I come non-fasting and skip the interpretation of my fasting sugar and triglycerides vs. having you be low for hours, and possible have a wreck on the way. It’s never worth it.

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Curious what test needs 18 hours, too.
Hope you can get away with 12!
I told my GP I wouldn’t be doing fasting unless absolutely necessary and I haven’t in many years. Found it was not worth messing up my sugars for a random BG test.
On fasting days I used to let me glucose ride slightly higher to be safe, and then would get told my fasting sugars were high. Of course I could have just taken a bit of insulin just before the test and still be fasting. Silliness.

I’m on a pump so fasting isn’t too difficult to manage. I ended up fasting 14 hours because I didn’t eat before the test.
The tests were minimal. A1c and lipid panel and urine protein gfr
Everything was normal
My total cholesterol has been creeping up higher.
I’ve been taking one cholestoff supplement.
My total cholesterol was177 and my Hdl was 63 ldl was calculated at 93.
So I’m under the wire but my lipids are higher than they used to be.