watchful

Adjective

• experiencing or accompanied by sleeplessness
  • insomniac old people
    
  • insomniac nights
    
  • lay sleepless all night
    
  • twenty watchful, weary, tedious nights- Shakespeare
    

• engaged in or accustomed to close observation
  • caught by a couple of alert cops
    
  • alert enough to spot the opportunity when it came
    
  • constantly alert and vigilant, like a sentinel on duty
    

Related words

• Synonyms: 
  insomniac , sleepless , alert
• Antonyms: 
  unalert , unwatchful , unvigilant