Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Condensed Statements of Operations and Comprehensive Loss [Abstract]
Revenue	$ 24,701	$ 20,067	$ 73,210	$ 54,093
Cost of goods sold	6,076	5,488	18,213	16,074
Gross profit	18,625	14,579	54,997	38,019
Operating expenses:
Research and development	6,867	4,711	19,611	11,232
Selling, general and administrative	25,049	19,202	68,792	54,652
Total operating expenses	31,916	23,913	88,403	65,884
Loss from operations	(13,291)	(9,334)	(33,406)	(27,865)
Interest income	42	249	183	951
Interest expense	(633)	(1,215)	(1,884)	(3,620)
Other income (expense), net	(3)	(15)	(11)	(74)
Net loss	(13,885)	(10,315)	(35,118)	(30,608)
Other comprehensive loss:
Unrealized gain (loss) on investments, net	(2)	(164)	(38)	150
Net change in other comprehensive loss	(2)	(164)	(38)	150
Net loss and comprehensive loss	$ (13,887)	$ (10,479)	$ (35,156)	$ (30,458)
Net loss per share, basic and diluted	$ (0.40)	$ (0.31)	$ (1.02)	$ (0.94)
Weighted average common shares used to compute net loss per share, basic and diluted	34,736,015	33,757,599	34,536,980	32,597,007