Direct Answer
Quest Diagnostics reports revenue across 2 business segments in its fiscal 2025 Form 10-K. Diagnostic Information Services Business is the largest, with $10.8 billion of revenue (98% of the total), followed by All Other at $250 million (2%).
How Does Quest Diagnostics Make Money?
Diagnostic Information Services Business supplies 98% of revenue, so Quest Diagnostics's results move mostly with that one business; the others matter more for diversification than for the headline number. Between fiscal 2024 and 2025, Diagnostic Information Services Business grew fastest (+12.2%) and All Other slowest (-3.1%), so the revenue mix tilts toward Diagnostic Information Services Business while that gap lasts.
| Segment | FY2025 revenue | FY2024 revenue | Share of revenue | Change |
|---|---|---|---|---|
| Diagnostic Information Services Business | $10.8 billion | $9.6 billion | 97.7% | 12.2% |
| All Other | $250 million | $258 million | 2.3% | -3.1% |
Which Quest Diagnostics Segments Earn the Most?
| Segment | FY2025 segment operating income | Segment margin |
|---|---|---|
| Diagnostic Information Services Business | $1.8 billion | 17.0% |
| All Other | $32 million | 12.8% |
Segment operating income is the profit measure Quest Diagnostics reports to its chief operating decision maker for each segment. It usually leaves out corporate costs that are not allocated to a segment, so the segments usually add up to more than consolidated operating income, and margins are comparable within Quest Diagnostics more safely than against another company.
What the Segment Figures Do Not Show
The rows above add up to 100% of Quest Diagnostics's reported revenue for fiscal 2025; the difference is intersegment eliminations, corporate revenue or items the company reports outside its segments. Segment definitions are management's choice and change when a company reorganizes, in which case it restates prior years in the next filing, so a multi-year comparison should use the figures from a single filing. Revenue shows where sales come from, not where profit or cash is earned: a small segment can carry most of the margin.
Where These Numbers Come From
Every figure on this page is a value Quest Diagnostics reported in the segment note and revenue disclosures of its Form 10-K filed February 26, 2026 (accession 0001022079-26-000015), read from the SEC's Financial Statement Data Sets. The prior-year column is the comparative figure from that same filing, so it reflects any restatement for a change in segments. Category names are the company's own XBRL labels, lightly reformatted for reading.
Rows that only total other rows (for example a "Products" line beside the individual products) are left out so nothing is counted twice. This page is educational and describes reported history for fiscal 2025; it is not a forecast or a recommendation.
Frequently Asked Questions
What are Quest Diagnostics's business segments?
In its fiscal 2025 Form 10-K, Quest Diagnostics reports revenue for Diagnostic Information Services Business and All Other.
Which part of Quest Diagnostics brings in the most revenue?
Diagnostic Information Services Business, with $10.8 billion of revenue in fiscal 2025, or 98% of the total.
Where does Quest Diagnostics report its segment results?
In the segment note to the financial statements in its Form 10-K, most recently filed February 26, 2026, alongside management's discussion of each segment's results.