What is the only ingredient required to make methamphetamine in every manufacturing process?

Pseudoephedrine is the only ingredient that is consistently required in every manufacturing process for methamphetamine. This substance is a common decongestant found in many over-the-counter medications. Due to its vital role in the synthesis of methamphetamine, it has been regulated in many areas to prevent illegal drug production.

While other substances, such as ephedrine, acetone, and lithium, may play roles in specific methamphetamine production methods, pseudoephedrine is the primary precursor ingredient across all known methods. This means that without pseudoephedrine, the chemical reactions necessary to produce methamphetamine cannot occur, whereas the other substances mentioned can vary depending on the specific approach taken in the manufacturing process.