The main organ that filters the blood in the human body is the kidney.

Key answer

  • The kidneys continuously filter the blood, removing waste products, excess water, and extra salts, then excrete them as urine.
  • Each kidney contains around a million tiny filters called nephrons that actually perform this cleaning process.
  • In many school-style multiple-choice questions, when asked “Which organ filters the blood?”, the expected answer is “kidney”.

Other organs that also filter

While the kidney is the primary blood filter, a couple of other organs help with more specific “filtering” roles:

  • Liver : Helps detoxify chemicals, metabolize drugs, and process nutrients from the blood coming from the digestive tract.
  • Spleen : Filters the blood to remove old or damaged red blood cells and helps the immune system by dealing with microorganisms.

So if the question is “Which organ filters the blood?” in a general biology or exam context, the best single answer is the kidney.

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