Solved cryptogram
Blood in your veins is dark red, never blue. The color you see is skin scattering the light.
Biology Facts, sourced to MedlinePlus.
What it means
Oxygen rich blood is bright scarlet and oxygen poor blood is a deep maroon, and neither is blue at any point. Veins look blue through the skin because longer wavelengths penetrate the tissue and are absorbed while shorter ones scatter back out. Anyone who has given blood has watched dark red come out of a vein that looked blue a moment earlier.
The claim comes from MedlinePlus, and the page it comes from was read on 2026-08-27 to confirm it still says this.
This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.
Solve it yourself
This fact is a cryptogram here: 72 letters over 18 different ones, graded easy.
- SourceMedlinePlus
- CollectionBiology Facts
- Difficultyeasy
- Length72 letters, 18 of them different
Nearby in the collection
The facts either side of this one.
- NHLBImedium, 74 letters
- NHLBIhard, 75 letters
- MedlinePlushard, 76 letters
- NCBI Bookshelfeasy, 75 letters
About as hard as this one
Scored closest to it by the model behind our guide to solving cryptograms.
- National Human Genome Research Instituteeasy, 77 letters
- NIDCDeasy, 74 letters
- Brain Research Bulletineasy, 74 letters
- NCBI Bookshelfeasy, 77 letters