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Glossary

What is magnesium stearate?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Magnesium stearate is the magnesium salt of stearic acid, a fatty acid from edible fats and oils. In supplements it works as a lubricant: it keeps powder from sticking to machinery during manufacturing, such as tablet pressing. FDA affirms it as generally recognized as safe for this use.1,2,3

Key facts

  • FDA affirms magnesium stearate as GRAS for use as a lubricant and release agent, a nutrient supplement and a processing aid, at levels within good manufacturing practice.1
  • The ingredient sold commercially is mainly magnesium stearate and magnesium palmitate in varying proportions, made from edible fats and oils.3
  • EFSA's 2018 re-evaluation found no safety concern at reported uses and use levels, and no need for a numerical acceptable daily intake.3
  • In the gut, salts like this are expected to split into fatty acids and magnesium.3
  • USDA organic rules allow it only in products labeled made with organic ingredients, not in products labeled organic.4

Why it is in your supplement

Powder blends can stick to the steel surfaces of tablet presses and other equipment. A lubricant stops that, and FDA defines the job of a lubricant and release agent as keeping ingredients and finished products from sticking to food contact surfaces.2,5

A 2010 review of tablet lubrication notes that lubricants such as magnesium stearate can also change a tablet's physical and chemical properties, so the amount used and the way it is mixed in are part of formulation work.5

What regulators have said

  • FDA: affirmed as generally recognized as safe (GRAS) as a direct food ingredient, at levels no higher than good manufacturing practice calls for.1
  • EFSA: in 2018 found magnesium salts of fatty acids (E 470b) of no safety concern at reported uses and use levels.3
  • European Union: permitted in solid food supplements such as capsules and tablets at the level needed for its purpose.3
  • USDA organic: allowed in made with organic products, prohibited in products labeled organic.4

These findings cover the uses and levels the regulators reviewed. EFSA saw no need to set a numerical daily limit, which is different from saying any amount is harmless.3

Where to find it on the label

Magnesium stearate is not a dietary ingredient, so FDA requires it in the ingredient list rather than the Supplement Facts panel. Look for it under Other ingredients, listed in order of weight with the other excipients.6,7

Questions people ask

Is magnesium stearate bad for you?

Regulators have not found it to be a concern at the amounts used. FDA lists it as GRAS for use as a lubricant, and EFSA's 2018 review found no safety concern at reported uses and use levels. If you prefer to avoid it, check the Other ingredients list.1,3,6

What is magnesium stearate made from?

From fatty acids in edible fats and oils, mostly stearic and palmitic acid, combined with magnesium. FDA's description is the magnesium salt of stearic acid from edible sources.1,3

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Sources

  1. Code of Federal Regulations, Title 21, Section 184.1440: Magnesium stearate. eCFR, current as of October 2026. Opened 2026-10-07.
  2. Code of Federal Regulations, Title 21, Section 170.3: Definitions (food additives). eCFR, current as of October 2026. Opened 2026-10-07.
  3. EFSA Panel on Food Additives and Nutrient Sources added to Food. Re-evaluation of sodium, potassium and calcium salts of fatty acids (E 470a) and magnesium salts of fatty acids (E 470b) as food additives. EFSA J. 2018;16(3):e05180. Opened 2026-10-07.
  4. Code of Federal Regulations, Title 7, Section 205.605: Nonagricultural substances allowed in or on processed products labeled organic or made with organic ingredients. eCFR, current as of October 2026. Opened 2026-10-07.
  5. Wang J, Wen H, Desai D. Lubrication in tablet formulations. Eur J Pharm Biopharm. 2010;75(1):1-15. Opened 2026-10-07.
  6. Code of Federal Regulations, Title 21, Section 101.4: Food; designation of ingredients. eCFR, current as of October 2026. Opened 2026-10-07.
  7. U.S. Food and Drug Administration. Dietary Supplement Labeling Guide: Chapter V. Ingredient Labeling. April 2005. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.