Chemically identical to glucose – blood sugar – dextrose is a simple sugar which is made from corn. It is a common food additive and is often found in processed foods.
Dextrose has a number of medical applications. It can be dissolved and given intravenously to people who are dehydrated or in need of extra nutrition. It can also be given as "rescue tablets" to diabetics who are experiencing hypoglycaemia.
Dextrose is also a popular athletic supplement. Because it is a simple sugar, it has a high glycemic index, meaning that it is digested quickly and the energy from the sugar is available straight away to the body.
Since exercise causes muscle damage, athletes like to take a post-workout protein and carb shake, which helps to encourage muscle healing during the critical 60 minute window following exercise. Dextrose is a popular ingredient in a post workout shake because it causes an insulin spike, which signals to the brain to send energy to the muscles, rather than to fat.
Dextrose as a supplement is available in powder form, but you can also buy dextrose tablets and capsules. If you are diabetic, dextrose should only be taken in the event that your blood sugar falls too low.