Among common sugars, fructose has the lowest glycemic index at 15, far below table sugar (sucrose) at 65 and pure glucose at 100. But if you expand the question to include sugar substitutes, several options score even lower. Erythritol, for example, registers a GI of just 1.
Which option makes the most sense for you depends on how you plan to use it, how it tastes, and whether you’re looking for a true sugar or are open to alternatives. Here’s how the full landscape breaks down.
How the Glycemic Index Scale Works
The glycemic index ranks carbohydrates on a scale of 0 to 100 based on how quickly they raise blood sugar after eating. Pure glucose sits at the top as the reference point at 100. Harvard Health classifies foods with a GI of 55 or below as low, 56 to 69 as moderate, and 70 or above as high. The lower the number, the slower and smaller the blood sugar spike.
GI Rankings for Common Sugars
Here’s how familiar sweeteners stack up:
- Fructose: GI of 15 (low)
- Coconut sugar: GI of 35 (low)
- Maple syrup: GI of 54 (low)
- Honey: GI of 61 (moderate)
- Table sugar (sucrose): GI of 65 (moderate)
- Glucose: GI of 100 (high)
Fructose is the clear winner among natural sugars. It’s the same sugar found naturally in fruit and honey, though in those foods it comes packaged with fiber, water, and other nutrients that further slow absorption.
Why Fructose Scores So Low
The reason fructose barely budges blood sugar comes down to how your body processes it. Unlike glucose, which enters your bloodstream quickly and can be used by virtually every cell, fructose takes a detour through your liver first. Your liver converts it into usable energy at a much slower pace, so blood sugar stays relatively stable. Fructose is also absorbed more slowly through the intestinal wall than glucose, which adds another layer of delay.
This sounds like great news, but there’s a catch. Concentrated fructose in large amounts (like high-fructose corn syrup in processed foods) puts extra strain on the liver and has been linked to increased fat storage and metabolic problems over time. The fructose in whole fruit isn’t a concern because you’re getting small amounts alongside fiber. But using pure fructose as a sweetener in large quantities isn’t necessarily a healthier choice just because it has a low GI.
Sugar Alcohols: Even Lower Numbers
If you’re open to sugar substitutes, sugar alcohols score dramatically lower than any natural sugar. These are carbohydrates that occur naturally in some fruits and fermented foods, though commercial versions are manufactured. They taste sweet but are only partially absorbed, which is why they barely register on the glycemic index.
- Erythritol: GI of 1, about 63% as sweet as sugar, with only 5% of the calories
- Mannitol: GI of 2, about 50% as sweet as sugar
- Isomalt: GI of 2, about 54% as sweet as sugar
- Lactitol: GI of 3, about 35% as sweet as sugar
- Sorbitol: GI of 4, about 58% as sweet as sugar, with roughly 60% of the calories
- Xylitol: GI of 12, about 97% as sweet as sugar, with 40% fewer calories
- Maltitol: GI of 35, about 75 to 90% as sweet as sugar, with roughly half the calories
Erythritol stands out because it combines the lowest GI with almost zero calories, and it causes fewer digestive side effects than other sugar alcohols. Most sugar alcohols can cause bloating, gas, or a laxative effect when consumed in moderate to large amounts because they ferment in the gut. Erythritol is mostly absorbed before it reaches the large intestine, so it’s better tolerated for most people.
Xylitol is the closest to sugar in taste and sweetness, making it a popular choice for baking and cooking. Its GI of 12 is still well within the low category.
Zero-Calorie Sweeteners With No GI Impact
Stevia and monk fruit extract technically sit at a GI of zero because they contain no carbohydrates at all. They pass through your body without affecting blood sugar in any measurable way. Both are plant-derived: stevia comes from the leaves of a South American plant, and monk fruit is a small melon native to Southeast Asia.
These work well in beverages, smoothies, and some baked goods, but they behave nothing like sugar in recipes that depend on sugar for structure or browning. They’re also intensely sweet in tiny amounts, so they require very different measurements. If you’re purely looking for the lowest possible blood sugar impact, these are as low as it gets, but they don’t function as sugars in the traditional sense.
Isomaltulose: A Slow-Release Alternative
Isomaltulose (sold under the brand name Palatinose) is a less well-known option worth considering. It’s made from sucrose but has a different molecular structure that your body breaks down much more slowly. Its GI ranges from about 44 to 58 depending on the specific formulation, placing it in the low-to-moderate range.
What makes isomaltulose interesting is the pattern of its blood sugar response. Rather than a sharp spike followed by a crash, it produces a gradual, sustained rise. The energy from isomaltulose is absorbed over a longer period compared to regular sugar. This makes it popular in sports nutrition products and specialty foods marketed for sustained energy. It tastes mildly sweet, roughly half as sweet as table sugar.
Allulose: Rare Sugar, Minimal Impact
Allulose is a rare sugar found naturally in tiny amounts in figs, raisins, and maple syrup. It tastes and behaves much like regular sugar in cooking, but your body absorbs very little of it. It provides roughly 10% of the calories of table sugar.
Clinical research published in BMJ Open Diabetes Research & Care found that a 10-gram dose of allulose consumed alongside regular sugar significantly reduced the insulin spike at 30 minutes compared to a placebo, and produced a dose-dependent reduction in overall insulin response. While no single standardized GI value has been established, its effect on blood sugar is minimal enough that the FDA allows products containing it to exclude allulose from the total sugar count on nutrition labels.
Choosing the Right Option
Your best choice depends on what you’re using it for. If you want a real sugar that behaves like sugar in cooking and baking, coconut sugar at a GI of 35 is the most practical low-GI option. Fructose scores lower at 15, but using large amounts of pure fructose carries its own metabolic trade-offs.
For sweetening coffee, tea, or yogurt, erythritol, xylitol, stevia, or monk fruit all keep blood sugar essentially flat. Erythritol and xylitol have the advantage of tasting and measuring more like sugar, while stevia and monk fruit require much smaller amounts. If digestive comfort is a priority, erythritol is the gentlest sugar alcohol, and stevia and monk fruit cause no GI issues at all.
For baking, allulose is gaining popularity because it caramelizes, dissolves, and adds moisture the way sugar does, all with a negligible blood sugar impact. It’s more expensive than other options and can be harder to find, but it’s the closest thing to a drop-in sugar replacement that also scores near the bottom of the glycemic index.