DL-alpha-tocopherol is the synthetic form of vitamin E. It is a racemic mix of eight stereoisomers, only one of which (RRR-alpha-tocopherol) occurs in nature and gets retained by the body. Per international unit (IU), this synthetic version has roughly half the biological activity of natural vitamin E (d-alpha-tocopherol). You will find it in multivitamins, standalone supplements, and fortified foods. Both forms act as antioxidants, but the synthetic type gets stored in tissues and processed by the liver less efficiently, so it is a weaker option for maintaining vitamin E status.
Most people take it inside a daily multi or on its own to help maintain ordinary immune and antioxidant defenses. Fat improves absorption, so take it with a meal that contains some fat. Labels usually state the dose in IU (for example, 30 IU or 400 IU), though clinicians often talk about vitamin E needs in milligrams of RRR-alpha-tocopherol equivalents.
High intakes above 1,000 IU per day can raise bleeding risk, especially if you also take blood-thinning medications. Avoid large doses before surgery.