v3.26.1

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2026	May 06, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
Document Transition Report	false
Entity File Number	001-39049
Entity Registrant Name	EXAGEN INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0434866
Entity Address, Address Line One	1261 Liberty Way
Entity Address, City or Town	Vista,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92081
City Area Code	(760)
Local Phone Number	560-1501
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	XGN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,159,839
Entity Central Index Key	0001274737
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
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Cover page.

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The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

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A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

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Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

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Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

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Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.

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Two-character EDGAR code representing the state or country of incorporation.

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Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

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The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

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Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.

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Indicates that the company is a Smaller Reporting Company (SRC).

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The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

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Local phone number for entity.

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Title of a 12(b) registered security.

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Name of the Exchange on which a security is registered.

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Trading symbol of an instrument as listed on an exchange.

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EXAGEN INC. 10-Q