I use stevia, and erythritol, both of which are recommended as diabetic friendly. They have no effect on glucose levels, and importantly if you're needing to lose weight - contain virtually no calories. My stevia is in liquid form, and the erythritol I use for baking is granulated (Sukrin Gold) or powdered (Natvia icing sugar) and these are available from Amazon UK.
Xylitol is also well recommended for baking - but be aware it can be
very harmful to dogs, even in tiny quantities.
Some sweeteners (including erythritol) are actually very high in carbohydrates, but these carbs are not absorbed by your body, so have no (or virtually no) effect on glucose levels.

But some sweeteners are extremely sweet and may be sold in granulated/powdered form with various starchy fillers to bulk them out, so read any nutritional information carefully!
Many sweeteners contain sugar alcohols, which can cause various gastric upsets if used in quantity, and these are alsounfortunately often used in diabetic products such as sweets and chocolate. So again you may need to do a little research regarding ingredients and their potential effects.
Also do a search through the low carb area of the forum, as this is a topic that frequently comes up, and you can see what other people here use and recommend
Robbity