My wife just started back on her doctor-recommended ketogenic diet (due to a medical history of high blood pressure and Crohn's disease in her family). She's to have reduced carbohydrates and sugars, and to use artificial sweeteners for anything she would normally add sugar to.

While making our morning coffee, I found a clear plastic container with what looks like stevia stored away - a taste confirms that it has a slightly different taste than the sugar I have on hand.

But I want to be absolutely sure before I recommend she use it in her baking - is there any surefire way to tell if this is stevia and not sugar?

Note: It may also possibly be Truvia.

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    Please note that the question is very clear - how can the asker determine the content of the jar. This is not the place to discuss medical issues or dietary choices, especially as they are unrelated to the question at hand.
    – Stephie
    Commented Jun 4, 2019 at 16:17

7 Answers 7


Don't throw it away. Worst case you use up the mystery sweetener on yourself, and use a new pack of Stevia for your wife and anything you share. That's what I recommend if you're not convinced by my solution or don't have sensitive kitchen scales.

At room temperature, sucrose (normal sugar) is very soluble in water: about 200 g of sugar will dissolve in 100 g of water.

It's harder to get a figure for the solubility of Stevia as it's not a single compound but a mixture of related compounds. However various patents claim "high solubility" stevia preparations of around 30 g per 100 g water, or around 1/7 as much.

This is enough of a difference to test: If (with plenty of stirring but no heat) the mystery sweetener will dissolve in an equal mass (weight) of water, it's sugar. If not it's stevia. This only works if you weigh it. You can't do this by volume.

You can always compare to known sugar; a comparison to know stevia is less useful unless it's identical, and brands evolve. The conclusion holds for fructose too (that's even more soluble), but glucose, which you're unlikely to have as pure powder at home, needs slightly more than its own weight of water to dissolve it.

Pure stevia is much sweeter than sugar, and when concentrated may have an aftertaste. It's also sold blended. When blended with other sweeteners the solubility test probably still applies (certainly in the case of erythritol, find in Truvia). Sometimes stevia is bulked out to make it a more direct substitute for sugar. The bulking agents may well be rather soluble and a source of carbohydrates (maltodextrin is sometimes used).

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    How do you know it's not something other than stevia... some mixture - sweet'n'low or one of those other chemical monstrosities?
    – Tetsujin
    Commented Jun 2, 2019 at 17:23
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    @Tetsujin the OP only offers two possibilities
    – Chris H
    Commented Jun 2, 2019 at 17:55
  • Speaking honestly, Truvia is also possible. Not sweet & low though. I'll add it to my question though just to be through.
    – Zibbobz
    Commented Jun 2, 2019 at 20:14
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    Truvia looks like a mixture of stevia and erythritol, in secret proportions. Erythritol is more soluble than stevia but the test should still work. I'd do it myself but I don't have any non-sugar sweeteners in the house.
    – Chris H
    Commented Jun 2, 2019 at 21:18
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    @jwenting, common sugar is sucrose, not glucose, whether it's from sugar cane or sugar beet. A molecule of sucrose consists of a molecule of glucose bonded to a molecule of fructose, but in terms of physical properties it's a stretch even to say sucrose is 50mol% glucose.
    – Chris H
    Commented Jun 4, 2019 at 5:55

Ants don't care about artificial sweeteners.

Make two piles: one of your mystery sweet stuff and one of real sugar (as a control to make sure there are ants around). Maybe moisten them some or make syrup. Leave them outside somewhere you see ants. Then check them later.

Carbohydrates (sugar) are fuel for all animals. Stevia has no food value. Ants taste things differently than we do. They only care about stuff with food value: real sugar. They will not go to artificial sweeteners.

Experiment on yourself.

Or you could use yourself as a guinea pig. Eat the ketogenic diet with your wife. When your ketostix are good and purple you are in ketosis. Then eat a hog load of the mystery powder. Sugar will break ketosis within 15 min and your ketostix will go back to white. If it is sweet and does not break ketosis then it is fine for the ketogenic diet. That is what she really wants to know, anyway.

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    Interesting, I'll have to test this on the maltodextrin component of Splenda. (Maltodextrin is probably the only component they might go for)
    – NSGod
    Commented Jun 2, 2019 at 22:46
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    Ketostix aren't a reliable method to determine whether you are in or out of ketosis. All they show is that, at some point in the past, your body was producing ketones, and now it's discarding them in your urine. It says nothing about the state you're in now. Having been in ketosis over 7 years, I could pee on one and it wouldn't turn at all, because my body knows how to use ketones, and doesn't discard them. While ingesting a large amount of sugar could raise insulin high enough to shut down ketone production, the body would still likely discard existing ones in urine.
    – NSGod
    Commented Jun 3, 2019 at 20:35
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    Stevia is not an artificial sweetener. It's a plant extract. I have no idea whether ants care for it, however.
    – JimmyJames
    Commented Jun 3, 2019 at 20:49
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    This is a really fascinating suggestion. Is there any reference available to validate that ants will completely ignore artificial sweeteners?
    – dwizum
    Commented Jun 5, 2019 at 17:28
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    @dwizum And if that's the case, do they also ignore stevia?
    – JimmyJames
    Commented Jun 5, 2019 at 19:40

This answer is specific to OP's situation, and doesn't apply for the general case where "getting it wrong" has fewer consequences.

is there any surefire way to tell if this is Stevia and not sugar?

No, there is no surefire way you can tell.

Within the bounds of an everyday kitchen, and lay-person knowledge; there is no method by which you will be 100% certain of the contents of the jar. As this is for the health of your partner, who has a medical condition - it is not worth taking any risk whatsoever.

Furthermore; testing that the majority of the jar is Stevia, does not ensure that the jar only contains Stevia.

The cost of a new jar of Stevia, is far lower than the cost of accidentally harming your partner. I would strongly recommend not to take any risk, and accept the cost of replacement as part of your transition to a new, better labelled life-style.

Of course, the existing jar does not have to go to waste, I'm sure you have plenty of neighbours and friends who will happily make use of a jar of "probably Stevia".

  • I do appreciate this comment as it is important to be cautious on an extremely strict diet - in this case, my partner's diet is not so strict (and I've edited my question to say so), but I still appreciate this answer.
    – Zibbobz
    Commented Jun 3, 2019 at 12:50

Wow, do not throw it away, especially if you have a scale or yeast handy. There are 2 easy methods to determine whether the unknown sweetener is sugar or not.

Try fermenting unknown sweetener with yeast

With the exception of lactose, yeast can feed on all "real" sugars, or at least the ones you'd normally keep in your kitchen. On the other hand, in all of my testing, I was unable to get any "artificial" sweeteners to be fermented by yeast. Those tests included Splenda (maltodextrin + Sucralose), erythritol, and even allulose (psicose). The same would likely be true for Stevia granular sweetener, as it's a mix of maltodextrin + stevia.

Use weight and taste to determine sweetener type

First of all, pure stevia powder that isn't cut with anything would be incredibly sweet (with possibly a bitter aftertaste): the sweetness is much more concentrated than sugar. Generally, pure sugar substitutes like stevia extract, sucralose, etc. are usually "cut" or bulked with less sweet ingredients like maltodextrin (hardly sweet at all) or erythritol (75% as sweet as sugar).


1 cup of sugar weighs around 200 g.

1 cup of Truvia (erythritol and stevia extract) should weigh around 224 g.*

1 cup of Swerve (erythritol, oligosaccharides and natural flavors) should weigh around 204 g.*

1 cup of Splenda (maltodextrin + sucralose) should weigh around 27 g (yes, it's that light).

1 cup of maltodextrin + stevia extract should also weigh around 27 g.

If she's ever used this sweetener for baking, then it's unlikely that it's Equal (aspartame), as that loses its sweetness when subjected to heat.

* Note that any sweetener that contains erythritol will be easily distinguished by the extreme cooling sensation it has on the tongue compared to other sweeteners. With Swerve in particular, I've found the that the sweetness sensation seems to linger for minutes after I've tasted it (provided I don't eat anything else). I don't get the same experience with Splenda. Sorry, I don't know how this compares with sugar (sucrose), as it's probably been 7 years or so since I've tasted it.

  • This paper suggests a bulk density of around 400g/l (100g/cup) for maltodextrin, which is more than you've got but still much less than white sugar. Do you have any idea of the variability in the packing fraction of sugar? If >=10% you wouldn't be able to tell the difference between sugar and Truvia/Swerve
    – Chris H
    Commented Jun 3, 2019 at 8:41
  • @ChrisH Swerve and Truvia both contain erythritol, which is easily distinguished by the cooling effect on the tongue compared to other sweeteners. Pure maltodextrin powder is likely around 100g/cup, but in the Splenda & other mixes where it's used, it's been highly "fluffed up". Sorry, not sure how to describe it. I mean, if I scooped out a cup of Splenda, and I worked at it, I could probably compress it down into about ¼ cup of volume, once I've forced out all the air. Hope that makes sense...
    – NSGod
    Commented Jun 3, 2019 at 13:39
  • Fluffing up would make sense for something that's essentially a bulking agent, and partly why I discounted the idea of using density as powder density is so variable. This could probably be achieved by controlling how it's dried.
    – Chris H
    Commented Jun 3, 2019 at 13:44

OK, this one will not be very practical, but I was inspired by one of the answers who claimed that

there is no surefire way to tell

But there is.

Sugar is optically active. A linearly polarized light beam will rotate while traveling through sugar. There is an instrument that measures this called polarimeter and, actually, its main use in business is to measure sugar quality by this exact property.

So, if you somehow manage to get access to one, just check which of your substances does make the beam turn.

  • I've actually got access to enough kit to do this, and it wasn't my first thought. A well deserved +1
    – Chris H
    Commented Jun 4, 2019 at 16:45
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    surefire way : check both of their spectrums.
    – Mazura
    Commented Jun 5, 2019 at 22:00
  • ahh, nice to see a fella scientist :) Commented Jun 5, 2019 at 22:03

Put a pinch of each into a pan and heat it.

Real sugar will turn into brown and sticky caramel. Sweetener won't.

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    Actually, sugar alcohols (erythritol) do melt and carmelize like sugar. IIRC, they do have a different melting point than sugar, though, which might be a way to distinguish them...
    – NSGod
    Commented Jun 3, 2019 at 14:01

When I do keto, I can tell within a short period of time by the buzz, if something has sugar in it. So the easy solution is for you to do keto for a few days, then drink a cup of this stuff.


Mark mentions that this is susceptible to psychological error. Firstly, this indicates to me that Mark hasn't ever done a long term keto diet. I've gotten steak at a steak house, assumed it was just steak, and got a huge buzz from the steak. I asked, and later I found out they added sugar to it.

Nevertheless, the way around this is to do this as a double blind study - get 32 people, give have them all do Keto for a few days, then give them unlabeled cups of Stevia vs sugar water, and ask whether they experienced a sugar buzz or not. This should result in a statistically significant measurement concerning which is sugar and which is Stevia.

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    This is highly susceptible to psychosomatic effects, where you experience a buzz because you're expecting to experience a buzz. See also: people getting drunk off non-alcoholic beer.
    – Mark
    Commented Jun 4, 2019 at 1:20
  • @Mark Good idea, edited Commented Jun 4, 2019 at 1:34
  • Ah, I see Willk has a better "taste it and test it" method. Commented Jun 4, 2019 at 1:41
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    @Mark No way. It's like cocaine. Notice that you write "I believe" instead of "I know". Like, spinach gets this really sweet flavor after a few weeks. And carrots? oh my! Commented Jun 4, 2019 at 2:44
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    If the buzz hits within 30 seconds, it's psychosomatic. Sugar can't go from your mouth to your brain instantly.
    – Robyn
    Commented Jun 4, 2019 at 8:31

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