ScienceModernglobalhigh confidence

Vitamin K deficiency can slow blood clotting and cause more blood to accumulate under the skin as a bruise.

Notes on verification

Well-established physiological mechanism corroborated by multiple independent clinical/medical references including MSD Manuals and peer-reviewed overviews. [tier=gold indep_score=0.925 clusters=4 claim_tier=everyday | kind=empirical eligibility=high]

Sources