Monk Fruit vs. Allulose: A Patient's Guide to Two Sweeteners That Actually Work for Diabetes, GLP-1 Medications, and Keto

By James Whynot, MD

If you've been diagnosed with diabetes, started a GLP-1 medication like semaglutide or tirzepatide, or you're following a keto diet, you've probably already stood in the sweetener aisle wondering what's actually safe. Sugar substitutes have exploded in the last few years, and two names keep coming up: monk fruit and allulose. Patients ask me about them constantly, usually with the same question — "does this actually spike my blood sugar or not?"

The short answer is that both are good options for people managing blood sugar, watching their carbs, or trying to lose weight on a GLP-1 medication. But they're not identical, and knowing the difference matters for how you use them. Here's what the evidence actually shows, along with real products you can buy in bulk, in single packets for your bag or desk, and in liquid form for coffee or baking.

What Is Monk Fruit?

Monk fruit sweetener comes from Siraitia grosvenorii, a small melon-like fruit grown in southern China. The sweetness doesn't come from sugar at all — it comes from natural compounds called mogrosides, which can be roughly 100 to 250 times sweeter than table sugar, gram for gram. Because mogrosides themselves contain essentially no calories and aren't metabolized the way glucose is, pure monk fruit extract doesn't raise blood sugar or insulin levels. The FDA considers it Generally Recognized as Safe (GRAS).

Here's the catch: because mogrosides are so intensely sweet, almost no commercial product is 100% pure monk fruit — it would be unusably concentrated. Most brands blend it with a bulking agent, usually erythritol (a sugar alcohol), to give it a texture and volume closer to sugar. That blend is still very low-glycemic, but it's worth knowing what you're actually getting, because erythritol has its own considerations — it can cause bloating or loose stools in some people at higher doses, and some recent observational research has raised questions about erythritol and cardiovascular risk that are still being studied. If that gives you pause, look for monk fruit blended with allulose instead of erythritol (more on that below), or use it sparingly.

What Is Allulose?

Allulose is sometimes called a "rare sugar" because it occurs naturally in tiny amounts in figs, raisins, wheat, and maple syrup. Structurally it's very close to fructose, but your body absorbs it and then excretes most of it largely unmetabolized, so it doesn't get converted to energy the way regular sugar does. That's why it comes in at less than 10% of sugar's calories while still tasting about 70% as sweet, with a very close, non-bitter, non-cooling flavor profile — many patients tell me it's the first sugar substitute that actually tastes like sugar to them.

Because it isn't metabolized as a carbohydrate, allulose doesn't meaningfully raise blood glucose or insulin. In 2020, the FDA went a step further than it has for almost any other sweetener and issued guidance allowing allulose to be excluded entirely from both the "Total Sugars" and "Added Sugars" lines on the Nutrition Facts label, and it's typically counted as having essentially zero net carbs. That's a big deal if you're tracking numbers closely for diabetes or ketosis.

The main downside is gastrointestinal tolerance. In larger amounts — generally more than about 25–30 grams at a time for most people — allulose can cause gas, bloating, or loose stools, similar to sugar alcohols, even though it isn't one. Your tolerance usually builds with time, so the practical advice is to start with small amounts and increase gradually rather than swapping it in cup-for-cup on day one.

For Diabetes

Both monk fruit and allulose are reasonable choices for blood sugar management, and both are commonly recommended alongside diet and medication. Neither should meaningfully move your fasting or post-meal glucose when used in typical culinary amounts. That said, "doesn't spike blood sugar" isn't the same as "has zero effect on your health," so I'd still encourage moderation over habit — use these to make appropriate foods and drinks more enjoyable, not as a green light to increase how much sweetened food you eat overall. If you use a continuous glucose monitor, it's worth testing your own response to a specific product, since blended products (with erythritol, dextrose, or maltodextrin fillers) behave a little differently than pure allulose or pure monk fruit.

For Patients on GLP-1 Medications

This is where I get the most questions lately. If you're on semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound), or a similar medication, you already know these drugs slow gastric emptying and can cause nausea, bloating, or changes in bowel habits on their own. That matters here because allulose's main side effect — gas and loose stools in larger amounts — can stack on top of GI symptoms you may already be managing. My practical advice for GLP-1 patients is to start with smaller amounts of allulose than the label suggests and see how you tolerate it before using it regularly in coffee, protein shakes, or baking.

There's also an interesting research angle worth knowing about, even though it's not a reason to change your medication regimen: several animal studies, and some early human data, suggest allulose itself may modestly stimulate the body's own GLP-1 release and blunt the post-meal blood sugar rise after a carbohydrate-containing meal. It's a genuinely interesting area of nutrition science, but it's early-stage and nowhere near a substitute for prescribed GLP-1 therapy — think of it as a mildly favorable side effect of the sweetener, not a treatment.

Monk fruit doesn't have this same research base around GLP-1 secretion, but it also doesn't carry the same GI tolerance concerns, which can make it the gentler choice if your stomach is already sensitive on these medications — just watch for the erythritol-blend GI effects mentioned above.

For Keto

Both work well on keto, but allulose has the cleaner story: because the FDA allows it to be excluded from total and added sugars, most nutrition labels and tracking apps will show it as 0g net carbs, and it won't affect ketosis for the vast majority of people. Pure monk fruit extract is also essentially carb-free, but check the label on blended products — some monk fruit sweeteners use dextrose as a carrier instead of erythritol, and dextrose is real sugar that will count against your daily carbs and can raise blood glucose. If you're strict about macros, look for "pure monk fruit extract" or a monk fruit/allulose blend, and skip anything listing dextrose or maltodextrin near the top of the ingredient list.

Where to Buy Them: Bulk, Packets, and Liquid

You don't need to guess what's actually on shelves — here are real, widely available products in each format.

Bottom Line

Monk fruit and allulose are both legitimate, evidence-backed options if you're managing diabetes, adjusting to a GLP-1 medication, or eating keto — a real step up from the older generation of artificial sweeteners for most patients. Allulose has the edge for keto tracking and possibly a small metabolic bonus around GLP-1, but start low to build GI tolerance. Monk fruit is a gentler starting point if your stomach is sensitive, as long as you check whether it's blended with erythritol or dextrose. Either way, read the ingredient label, not just the front of the package, and bring your specific product to your next visit if you want to go over it together — especially if you're titrating a GLP-1 medication or fine-tuning insulin dosing around meals.