One cup of raw raspberries (about 123 grams) contains roughly 5.4 grams of sugar, making them one of the lowest-sugar fruits you can eat. That’s less sugar than you’d find in a single teaspoon of table sugar (which contains about 4 grams), spread across an entire generous serving of fruit.
Sugar Per Serving and Per 100 Grams
A standard one-cup serving of fresh raspberries weighs about 123 grams and delivers 5.4 grams of total sugar alongside 14.7 grams of total carbohydrates. Per 100 grams, that works out to approximately 4.4 grams of sugar. The sugars in raspberries are a natural mix of glucose and sucrose, with glucose levels ranging from about 1.4 to 2.5 grams per 100 grams and sucrose hovering around 0.85 to 1.1 grams per 100 grams, depending on the variety.
How Raspberries Compare to Other Berries
Raspberries sit at the bottom of the sugar scale among popular berries. Here’s how a one-cup serving stacks up:
- Raspberries (123g): 5.4g sugar, 14.7g total carbs
- Strawberries (152g): 7.4g sugar, 11.7g total carbs
- Blueberries (148g): 14.7g sugar, 21.4g total carbs
Blueberries contain nearly three times the sugar of raspberries per cup. Strawberries fall in the middle, though their total carbohydrate count is actually slightly lower because a cup of strawberry halves has less dense fruit matter. If you’re specifically watching sugar intake, raspberries give you the most volume for the least sugar of any common berry.
Why Raspberries Are High in Fiber
What makes raspberries especially interesting from a carb perspective is their fiber content. Of those 14.7 grams of total carbohydrates per cup, a large portion is dietary fiber. If you subtract fiber from total carbs to get “net carbs” (the carbohydrates your body actually absorbs as energy), raspberries land around 7 grams of net carbs per cup. That high fiber-to-sugar ratio is unusual for fruit and is one reason raspberries are a go-to for people on low-carb or ketogenic diets, where the typical daily carb limit is 20 to 30 grams. A half-cup of raspberries fits comfortably within that range.
Glycemic Index and Blood Sugar Effects
Raspberries have a glycemic index of 30, which places them firmly in the low-GI category (anything under 55 is considered low). But the real story goes beyond the GI number. Multiple clinical trials have found that adding raspberries to a meal actually blunts the blood sugar spike you’d otherwise get from that meal’s carbohydrates.
In one crossover trial with 16 participants, adding 140 grams of red raspberries to a high-glycemic breakfast cereal lowered the blood sugar peak by about 11 mg/dL compared to eating the cereal alone, and by about 13 mg/dL compared to adding an equivalent amount of plain sugar. In other words, the raspberries didn’t just avoid raising blood sugar. They actively reduced the spike from the other food on the plate.
Larger studies have shown similar patterns. In a trial with 30 overweight adults, adding freeze-dried raspberry powder to a high-carb, moderate-fat breakfast significantly lowered both blood sugar and insulin peaks after the meal. Another study in 25 adults with type 2 diabetes found that 250 grams of pureed raspberries added to a fast-food-style breakfast reduced blood sugar levels at both the two-hour and four-hour marks. The fiber, polyphenols, and other plant compounds in raspberries appear to slow carbohydrate absorption and improve how the body handles glucose after eating.
Red vs. Black Raspberries
Most raspberries sold in grocery stores are red varieties, but black raspberries (a distinct species, not blackberries) have a slightly different nutritional profile. Research comparing the two found that black raspberries contain higher levels of glucose, polyphenols, and flavonoids than red raspberries. They also pack more calcium and magnesium. The sugar difference between the two is modest, though. Both types remain low-sugar fruits, and black raspberries’ higher concentration of plant compounds may offer additional antioxidant benefits.
Fitting Raspberries Into a Low-Sugar Diet
For people managing diabetes or following a ketogenic diet, raspberries are one of the safest fruit choices. A half-cup serving keeps you at roughly 3.5 grams of net carbs, which leaves plenty of room within a 20-to-30-gram daily carb budget. Even a full cup is manageable for most low-carb approaches.
Because raspberries actively moderate blood sugar response rather than just being neutral, they pair well with higher-carb foods. Adding them to oatmeal, yogurt, or cereal can reduce the glycemic impact of the overall meal. Fresh, frozen, and freeze-dried raspberries all appear to produce these effects in studies, so choose whichever form is most convenient. Frozen raspberries have the same nutritional profile as fresh since they’re typically frozen at peak ripeness. Just check the label on any packaged or dried varieties to make sure no sugar has been added during processing.