Weston's downgrade still values Novo Nordisk stock above its current share price of $47 and change, however. Moreover, Novo Nordisk stock currently costs less than 14 times earnings.

Novo Nordisk stock was downgraded to Neutral from Buy by UBS analysts, who cited the threat posed by its U.S. rival.

Novo Nordisk's U.S.-listed shares shed a third of their value last week after the company cut its full-year outlook and named a new CEO. Monitor these key chart levels.