Use 'haggard' to describe someone looking very tired and possibly stressed or unwell. She had a haggard appearance after working three night shifts in a row.
Pro Tip 2/3
Not Just Age
'Haggard' doesn't imply that someone is old, but that they look worn out temporarily. Despite his youth, the marathon left him looking haggard.
Pro Tip 3/3
Intensity
The word often conveys a strong change, not just slight tiredness. After the earthquake, survivors emerged haggard from the rubble.