Magnesium sulfate heptahydrate is a hydrate that is the heptahydrate form of magnesium sulfate. It has a role as a laxative and a cathartic. It is a magnesium salt and a hydrate. It contains a magnesium sulfate.

Used as a food fortifier. According to Chinese regulations, it can be used in dairy products at a dosage of 3–7 g/kg; in beverages and milk drinks at 1.4–2.8 g/kg; and in mineral beverages with a maximum usage level of 0.05 g/kg.

Mostly used with calcium salts for water in brewing yeast. Adding 4.4 g per 100 L of water increases hardness by 1 degree; excessive use causes bitterness and produces hydrogen sulfide odor.Used in leather tanning, explosives, paper manufacturing, porcelain, fertilizers, as an oral laxative in medicine, and as an additive in mineral water.

Magnesium sulfate is used as a fertilizer in agriculture, since magnesium is one of the main components of chlorophyll. It is commonly applied to potted plants or magnesium-deficient crops such as tomatoes, potatoes, roses, etc.The advantage of magnesium sulfate over other fertilizers is its high solubility.It is also used as bath salt.