Mannitol (also referred to as mannite or manna sugar) is a white, crystalline solid with the chemical formula C6H8(OH)6. It was originally isolated from the secretions of the flowering ash and called manna after its resemblance to the Biblical food. In plants, it is used to induce osmotic stress. It has several industrial uses, but is mainly used to produce tablets of medicine.

Uses
Medical uses
Mannitol is used clinically in osmotherapy to reduce acutely raised intracranial pressure until more definitive treatment can be applied, e.g., after head trauma. It is also used to treat patients with oliguric renal failure. It is administered intravenously, and is filtered by the glomeruli of the kidney, but is incapable of being reabsorbed from the renal tubule, resulting in decreased water and Na+ reabsorption via its osmotic effect. Consequently, mannitol increases water and Na+ excretion, thereby decreasing extracellular fluid volume.
Mannitol can also be used as a facilitating agent for the transportation of pharmaceuticals directly into the brain.
Mannitol is commonly used in the circuit prime of a heart lung machine during cardiopulmonary bypass.
Mannitol is also the basis of Bronchitol which was developed by the Australian pharmaceutical company Pharmaxis as a treatment for cystic fibrosis and bronchiectasis.
Mannitol is also the first drug of choice for the treatment of acute glaucoma in veterinary medicine.

Food
Mannitol increases blood glucose to a lesser extent than sucrose (thus having a relatively low glycemic index) and is therefore used as a sweetener for people with diabetes, and in chewing gums. Although mannitol has a higher heat of solution than most sugar alcohols, its comparatively low solubility reduces the cooling effect usually found in mint candies and gums. However, when mannitol is completely dissolved in a product, it induces a strong cooling effect. Also, it has a very low hygroscopicity- it does not pick up water from the air until the humidity level is 98%.

Analytical chemistry
Mannitol can be used to form a complex with boric acid. This increases the acid strength of the boric acid permitting better precision in volumetric analysis of this acid.