Common supplement fillers are inert substances added to capsules or tablets to add mass, improve manufacturing properties, and help ensure a consistent dosage. When people discuss common supplement fillers, they are usually talking about diluents, binders, flow agents, and related inactive ingredients. Examples you might encounter include microcrystalline cellulose, lactose, starch, dicalcium phosphate, calcium carbonate, and silicon dioxide (silica). Some products also use alternative capsule shells, such as hydroxypropyl methylcellulose (HPMC) instead of gelatin. This kind of terminology helps distinguish the active ingredient from the other substances in a product. These fillers serve practical roles in production and packaging. They help tablets hold together, fill space so the dosage is consistent from one unit to the next, improve the ease of manufacturing, and can contribute to shelf stability. Because they are not the active ingredients, they are considered part of the formulation rather than the primary component being delivered. Understanding the role of these common supplement fillers can make it easier to compare products on a like-for-like basis. Tips to read labels and compare products begin with checking the ingredient list for inactive ingredients or excipients. Look for the names of common fillers such as cellulose derivatives, lactose, starch, calcium salts, silica, or magnesium stearate. Be mindful of fillers that may be of particular concern to you, such as lactose if you have dairy sensitivities or gluten-containing starch if you avoid gluten. Note the serving size and how much of the product is made up by active ingredient versus fillers, and watch for other additives like colorants or coatings that may be listed separately. To choose safer supplements and minimize exposure to unwanted additives, favor products with clear, complete labeling and simpler excipient lists. If you prefer to avoid certain ingredients, prioritize items that use widely recognized, well-documented fillers or plant-based capsule options. Look for third-party testing or certifications as an extra layer of assurance, and consider keeping a personal reference list of fillers you want to avoid. If you’re unsure about a particular ingredient, consulting with a pharmacist or the product manufacturer can help clarify how the fillers are used in that formulation.
