Stop fasting for your labwork? Maybe...

Patrick Krupka, DC, CFMP:

So I was listening to another clinician talk recently about getting lab work done in a non-fasted state. And you guys know, things like cholesterol and blood sugar and things like that, when we send you to the lab for those, we generally want you to be fasting when you go into the lab. 6, 8, 10 hours without eating, you can certainly have water, but we want a decent amount of time without food consumption before you go into the lab and have those drawn. So there's a little bit of a push now to say, look, why don't we just do labs in the condition in which people live? Most people don't spend most of their time in the fasted state. Yes, you wake up that way, but then you eat, and then later you eat, and then later you eat again, and you snack a little bit, and then you exercise, and then you eat again, and then you go back to bed.

So most of your time is not spent in the fasting state, most of your time is spent in some version of what we loosely call the fed state. So some doctors are saying, some of the functional medicine doctors are saying, look, why don't we take a look at their labs in a non-fasted state and see what they look like, because that's the state they're in more often than not. I don't really disagree with that. I think that's kind of a cool idea. But there are some pros and cons that you need to be aware of before you go do this. Let me give you blood sugar as an example. We know where blood sugar should be when you are not fasted, right? If you eat a responsibly sized and comprised meal, that's not going to like... You're not eating donuts and coke, right? But you're eating steak and veggies and maybe some starch in there, something like that. A mixed meal, well-balanced.

We know that your blood sugar is probably going to go up into the 130s. Maybe you'll hit 140 within an hour or two of eating that meal, and then it should relatively quickly come back down into the low hundreds, and then settle back down into that 70 to 90 range that we want to see when you're fasting. So we know what fasting blood sugar should look like. We know what recently fed, we call it postprandial, which is after a meal. We know what postprandial blood sugar should look like. If any of you have been pregnant and gone through the glucose tolerance test where you drink that awful nasty syrupy stuff, and then they draw your blood every hour for several hours afterwards, and they watch your blood sugar come up and they go back down again. We know what that curve should look like.

Now, I gave you an example of eating a well comprised balanced meal. When you drink a 50 or 75 gram load of glucose, that's unopposed by anything else, I think that's an unnatural situation. I think you're asking for trouble. I think it's torture to make people go through that. But, I'm using it as an example, right? We know what that curve should look like. So in the case of blood sugar, testing someone in the postprandial or fed state, would make some sense. I mean, that's why we have continuous glucose monitors now that you put on your arm and it just constantly reads your blood sugar and you just wave a meter over it and it gives you a reading. You can see how you react after eating rice or after eating a banana or after having a steak or a handful of macadamias, whatever. You can see how you react to that. But we have something to compare it to. Like we know what it's supposed to be, there's a normal range for that, and you can see if you're within or outside of that. So it does make some sense.

Now, let's take it to the cholesterol panel. That's a different animal. Yes, your cholesterol is going to be different after you've eaten a meal or a snack, whatever else. It could be different after a major stressful incident. Your body dumps blood sugar and fat in your bloodstream as part of the fight or flight response. So there are things in your daily life that can make that look different than it would in the fasted state, and it can be very interesting to see that in a particular patient, and to see how it changes with different meals. Now, the downside of doing that. We don't have a good measure for what that should look like in a healthy person after a balanced meal. There's not enough research out there to say, okay, here's what it should look like fasted. Here's what it should look like after a well-balanced meal in a healthy person that manages it properly. The information's just not there.

So what you're going to end up with is a lab test that shows a higher than fasted cholesterol panel, and likely a different blend of ratios when you're looking at HDL and LDL and triglycerides in that panel, because you've eaten. The lab is going to compare it to a fasted sample. Your other doctors when they glance at that, are going to think that's a fasted sample. They don't have anything else to compare it to. Even if they know you didn't fast, they're going to want to compare that to the fasting numbers, and you are likely going to get a diagnosis of hypercholesterolemia, even though it's not legit, because it wasn't a fasting sample. Once you are given that diagnosis, or once those numbers are in your chart, and an insurance company looks at it or something, it's very difficult to undo the impression that gives an auditor or an actuary person at the insurance company or someone like that, they're going to look at it as inappropriate cholesterol.

So when you do a test like that, the upside of it is, you get some interesting information you'll learn a little bit about how different meals affect you. The downside is, other people aren't going to see it that way. They're going to look at it like it's a legitimate cholesterol panel, and they are either going to diagnose or prescribe, based on whether or not you're inside the range for a fasting sample, even though you're not fasting. And that can occur with lots of different tests. There are other tests where we really don't solidly know what eating meals does to that, CRP, homocysteine levels, certain liver markers. There are going to be a lots of markers where we question the relevance of a non-fasted sample. Now, it may be more relevant than a fasted sample, but the system isn't set up yet to evaluate it or interpret it that way. It will be interpreted as a fasting sample. They can't help themselves.

I get labs from patients where I look at it and I'm starting to think, oh my gosh, we've got all this stuff going on, and I'll look up at the top and where it says fasting yes or no, it says, no, they weren't fasted for that. I have to force myself to ignore all the results that are going to be influenced by their meal, and not pay attention to those. It's pretty difficult for a lot of doctors to do that. They want to take action based on the results they see, and it's hard for them to really get into their head that these were not fasting samples, I can't act on that. So just be aware. There are pros and cons to this new approach. I think we'll get to the point where there will be fasting ranges, and non-fasting ranges for these things. But right now we're just not quite there yet. So, do it if you like. I think the data is going to be very interesting. I think the only way we're going to get there is for people to start doing this.

But just understand early on, you may run into some issues with getting diagnoses that are just not legitimate, because your doctor saw a non-fasting sample and acted like it was a fasting sample. So, FYI, just be aware. If your doctor has recommended that to you, let me know. Throw something in the comments and let me know, I'd be curious. It's not all that common yet. But in the functional medicine space, there's a lot of talk about it, it's becoming more common. All right, let me know what you know.


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