What Color Is Blood Without Cells? Understanding Plasma

If you remove all cellular components (red cells, white cells, platelets) from blood, the remaining fluid—plasma—is a pale yellow (straw-colored) liquid.

Why Blood Appears Red

• Oxygenated blood (arterial): Bright red — hemoglobin (Hb) bound to O₂ (oxyhemoglobin).
• Deoxygenated blood (venous): Dark red/maroon — Hb without O₂ (deoxyhemoglobin).
• Color is entirely due to hemoglobin inside red blood cells (RBCs). RBCs constitute ~45% of blood volume (hematocrit).

Plasma Composition

• ~90% water.
• ~7% proteins (albumin, globulins, fibrinogen, clotting factors).
• ~2% electrolytes, nutrients, waste, hormones, gases.
• Yellow hue comes from bilirubin (hemoglobin breakdown product), carotenoids (diet), and flavins.

Serum vs. Plasma

• Plasma: Anticoagulated blood spun down — contains fibrinogen.
• Serum: Clotted blood spun down — fibrinogen consumed; otherwise similar color.

Clinical Note

Markedly yellow plasma (icteric) suggests elevated bilirubin (hemolysis, liver disease). Milky/turbid plasma indicates hypertriglyceridemia (lipemia). These are visual clues to pathology.