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Diabetes Knowledge

Is my diet soda really sugar-free? Check its sugar!

4/28/2015 by Scott Johnson

Is my diet soda really sugar-free? Check its sugar!

You ordered Diet Coke but is that what arrived? It tastes ... funny. But you're not sure. Do your lips feel sticky? Or is that your imagination?

Sugar-free or sugar-bomb? Sometimes it's hard to tell!

Living with diabetes, the difference between the Diet Coke we ordered and the regular Coke we're served isn't just a few extra calories. It can mean smooth sailing with our blood sugars or a day spent struggling to recover from the mix-up.

Most of the time I can tell the difference between the two, but sometimes the mix is so awful that I just don't know. Has it ever happened to you? Have you ever had a drink that you suspected might not be diet, but just weren't sure?

The little things we try

Being a victim of the Diet Coke order gone wrong, a.k.a "The Sugar Bomb," is a hard lesson to swallow. So I've built safety checks into my drink orders, and sometimes they help. Some examples:

  • I always take a sip of my Diet Coke before pulling away from the drive-thru window (if it's not diet or if it tastes weird, I still have time to ask them about it).
  • Whenever possible I try to watch the server or attendant fill my drink cup, to make sure it's positioned under the proper fountain nozzle. This one is hard, though, because perspective and angles can make it really difficult to tell.
  • I annunciate like crazy. "I'd like a large DIIIIIIIIIIIIIIEEEEEEEEEEETTTTTT Coke, please."
  • And there's nothing like being at a place where I can fill my own drink. Plus, unlimited refills? Yes, please!

The awkward ask

There are times, though, when it's not possible to avoid a conversation with the server or employee. I hate being a high-maintenance patron – but not as much as I hate going thirsty or running high blood sugars.

So I politely ask them to double-check and make sure it's diet. I've never had any trouble or pain-in-the-ass attitude from this. If they give me any hesitation, I explain my diabetes and they instantly understand.

Sometimes the new drink tastes completely different, and it's clear the first one wasn't diet, and sometimes it tastes exactly the same. In which case, the mix is really bad, or...

It's the wrong box

There have been four or five times in my life where I've filled my own drink cup directly from the fountain machine and I was sure I selected Diet Coke, yet I was also certain that what came out of the nozzle was not diet soda.

How is this possible?

The drink machines we see are only the front side of a complicated system with lots of tubes and hoses. Here's one behind the scenes example.

Drink station connections

Each flavor choice up front leads to a box of concentrated flavor syrup in the back. They are connected with a hose that delivers the flavored syrup to the nozzle, picking up chilled carbonated water on the way. At the end, assuming all of the settings are correct, we get a delicious beverage!

If you see many flavors up front, you can be sure there is a big thing like this in the back.

Drink station shelving with boxes of post mix flavor syrup

You can see below, there is a labeled hose leading to a labeled box.

I've seen a few different organization systems used to try and keep this all straight, but at the end of the day, it all depends on the person changing the empty box.

We are counting on them to put the correct box there and connect the right hose.

Labeled hose leading to a labeled box

Do you see any opportunity for error there? Especially for employees who don't think there's much difference between regular soda and diet soda? All it takes is for some sleepy, overworked person to put the wrong box in the wrong place and connect that hose. We're flying high.

Literally. And that's exactly what's happened to me when I've noticed in time. After some discussion with the store manager, they go check the connection, and sure enough, it's connected to a regular soda box.

So how can you really know for sure?

There are three ways I can think of to be sure you don't get accidentally sugar-bombed by a Diet Coke order gone wrong. 1) Drink water (ok, that's really healthy, but no fun at all) 2) If possible, get the drink directly from the can or bottle, or 3) Check its sugar!

"What? Check a drink's sugar?"


Most of the time you can actually do a BG check with the drink to be sure. Ilka and I did checks with a handful of different meters, and here's what we found.

Note: This will affect your meter averages and reporting (because you're testing soda, not your blood...). Where possible, I'll include instructions for marking the test as a "control" reading which will be ignored in your meter statistics, but not all meters allow it. So be aware before you try this.

Accu-Chek Aviva Plus

Coke: 546 mg/dl

Diet Coke: LO (Blood glucose may be lower than the measuring range of the system)

Control: It is possible to mark a reading as a special event by pressing either of the arrow keys, but it is not possible to manually mark a control reading.

Results from testing regular Coke and Diet Coke with an accu-chek Aviva

Bayer Contour

Coke: 106 mg/dl

Diet Coke: LO (test result is below 50 mg/dl)

Control: It is possible to mark a reading as a unique event by pressing either of the arrow keys until a logbook icon appears, then press "M". It is not possible to manually mark a control reading.

Test results from Bayer Contour check of regular soda

OneTouch UltraMini

Coke: HI (over 600 mg/dl)

Diet Coke: Er 4 (sample improperly applied, or there may be a problem with the meter, or there may be a problem with the strip, or you have high blood glucose and have tested in an environment near the low end of the system's operating temperature range (43-111°F)).

Control: Insert a test strip, but before applying anything to the strip press ↑ so that 'CtL' appears in the upper right corner of the display. Results marked with 'CtL' are not stored in the meter's memory.

Results from the OneTouch UltraMini Cola Test

OneTouch UltraSmart

Coke: HIGH GLUCOSE (You may have a very high blood glucose level, exceeding 600 mg/dL)

Diet Coke: Error 4, Strip Problem (sample improperly applied, or there may be a problem with the strip, or you have high blood glucose and have tested in an environment near the low end of the system's operating temperature range (43-111°F)).

Control: Insert a test strip, but before applying anything to the strip use ↑ to select "Control Solution" in the display. Marked control solution tests will not be included in averages.

Results from the OneTouch UltraSmart Cola Test


Coke: 212 mg/dL (& control solution icon)

Diet Coke: Er 6 (The test strip has taken too long to generate a signal)

Control: Control solution is automatically detected and a Control Solution icon is displayed.

Results from iBGStar Cola Test

That's what happened when I tried testing both regular Coke and Diet Coke with the meters I had here. You should give it a try with your meter if you can spare a test strip or two. Unfortunately, I know all too well that we can't often spare those pricey test strips.

But there's another way which can be a lot cheaper.

Hello, Diastix!

Before measuring blood sugar we had to measure something that feels kind of gross to talk about alongside Diet Coke...

Box of Bayer's Keto-Diastix for measuring Ketones and Glucose in urine

These test strips are still commercially available over the counter for pretty cheap.

This box, for example, which can be used to measure both ketones and glucose, is listed at Amazon for about $25. Each of these strips can also be cut in half (or smaller) if you really want to pinch pennies.

For a few dollars cheaper, you can get the strips that just measure glucose, which is all you'd need to check your drinks. But I personally think it never hurts to have some ketone strips around.

These strips can be dipped right into your drink, or you can use your straw to put a drop on it, and if your soda is not sugar-free, the glucose testing pad will turn noticeably darker within 30 seconds.

When in doubt, check it out

I hope some of these ideas might help if you're battling the Diet Coke order gone wrong. Like many things with diabetes, once you have a little bit of know-how and do some detective work you can make an informed decision about what to do.

Unanswered questions

There are some situations where I'm not sure what to do or expect.

What about those things bartenders use? You know, the contraption on the end of a hose that has a bunch of buttons on it for the different flavors? It's called a Soda gun. Drinks never taste good coming out of those nasty things.

If someone orders a regular Fanta Orange right before I order my Diet Coke, isn't there residual Fanta Orange in the tube before my Diet Coke comes out? I mean, I can taste the Fanta Orange, yo! How much sugar am I getting?

I bet good bartenders flush the line a little before serving the next drink. But I bet not all bartenders are good bartenders...

And what about those super fancy Coca-Cola Freestyle machines? I really enjoy using them, but I don't know how they work. I hear they use flavor cartridges, almost like an inkjet printer. But it's all coming out of the same nozzle, man! Same problem as the nasty bartender drink-dongle! And I also heard that the flavor syrups have sugar...

Ok, ok, ok. I'm starting to overthink things here. Time to have a Diet Coke and relax... Cheers, Monster Tamers!

The mySugr website does not provide medical or legal advice. mySugr blog articles are not scientific articles, but intended for informational purposes only.
Medical or nutritional information on the mySugr website is not intended to replace professional medical advice, diagnosis or treatment. Always consult a physician or health care provider with any questions you may have regarding a medical condition.

Scott Johnson

Almost famous for being a Diet Coke fanatic, Scott is the Patient Success Manager, US for mySugr and has lived well with diabetes for over 40 years. He's an active pioneer in the diabetes social media space and along with his work at mySugr, he manages his award-winning blog, when time allows.