After magnesium stearate, two more names dominate the Other Ingredients line across categories: silicon dioxide and some form of cellulose. Like the stearate, they are quiet, functional, and frequently misread as filler in the pejorative sense. Reading the label means knowing the role each one plays.
Silicon dioxide is an anticaking and flow agent. Powders absorb moisture and clump; a small amount of silicon dioxide keeps them free-flowing so they measure and fill evenly. On the label it usually appears late in the descending-weight order, consistent with the small quantity its job requires.
Cellulose appears in several guises. Microcrystalline cellulose is a common binder and bulking agent that gives a tablet structure or fills out a capsule. Hydroxypropyl methylcellulose, sometimes shown as HPMC or vegetable cellulose, is a frequent capsule shell material and an alternative to gelatin. The same plant-derived family, different jobs depending on where it sits.
The word filler tends to carry a negative charge it does not deserve. Bulking agents exist because a precisely measured active may be a tiny amount of powder that cannot, on its own, fill a capsule or form a tablet. Something has to occupy the rest of the volume. That something is a filler in the literal, neutral sense.
The reading habit is the same one we apply everywhere: name the function, check the position in the weight order, and resist letting a loaded word do the analysis. Silicon dioxide keeps powder flowing; cellulose binds, bulks, or forms the shell. Whether any specific excipient suits an individual is a matter for a qualified healthcare professional, not for the connotations of the word filler.