Your body produces 2 million red blood cells every second — they live for only 4 months
Red blood cells are produced in bone marrow at a rate of approximately 2 million per second — that's 172 billion per day. Each red blood cell lives for about 100–120 days before being broken down by the spleen and liver. The iron from destroyed red cells is recycled for new ones. At any given moment, you have about 25 trillion red blood cells circulating, each making approximately 75,000 circuits of your body before dying. A single drop of blood contains 5–10 million red blood cells.
The scale of this internal production line — 2 million cells per second, running continuously, every second of your life — makes the body's quiet manufacturing scale feel almost industrial. Most of us have never had cause to think about what 2 million of anything per second actually means.
“Your body makes 2 million red blood cells per second — 172 billion per day. Each lives 4 months, makes 75,000 circuits of your body, then is broken down and recycled. This runs every second of your life. 🔴 #OddlyHuman”