Yes, up is a Scrabble word!
...and is worth 4 points in Scrabble, and 6 points in Words with Friends
up
Adverb
1. Spatially or metaphorically from a lower to a higher position
2. To a higher intensity
3. Nearer to the speaker
4. To a more central or a more northerly place
5. To a later time
Adjective
1. Being or moving higher in position or greater in some value; being above a former position or level
2. Out of bed
3. Getting higher or more vigorous
4. Extending or moving toward a higher place
5. (usually followed by `on' or `for') in readiness
6. Open
7. (used of computers) operating properly
8. Used up
Verb
1. Raise