Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Precision oncology testing	$ 28,837	$ 14,191
Development services	7,818	2,501
Total revenue	36,655	16,692
Costs and operating expenses:
Cost of precision oncology testing	11,023	8,045
Cost of development services	2,512	1,208
Research and development expense	16,316	8,255
Sales and marketing expense	17,807	11,312
General and administrative expense	12,661	6,519
Total costs and operating expenses	60,319	35,339
Loss from operations	(23,664)	(18,647)
Interest income	2,485	985
Interest expense	(293)	(331)
Other income (expense), net	147	4,149
Loss before provision for income taxes	(21,325)	(13,844)
Provision for income taxes	26	0
Net loss	(21,351)	(13,844)
Fair value adjustment of redeemable noncontrolling interest	(4,700)	0
Net loss attributable to Guardant Health, Inc. common stockholders	$ (26,051)	$ (13,844)
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.30)	$ (1.16)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	85,935	11,920