The archive · Health & Care · Product decision · 2021–2026
OpenEvidence's doctor-first bet: free AI search to 758K doctors, $12B valuation
OpenEvidence gives US doctors a free, ad-supported AI medical search tool; 40%+ of US physicians use it daily, and a $250M Series D valued it at $12B.
OpenEvidence
What the business is
AI-powered medical search and decision-support platform that answers clinicians' questions from peer-reviewed journals and guidelines with citations; free to verified doctors and ad-supported.
Starting capital：~$700M total: $210M Series B (Jul 2025, GV and Kleiner), $200M Series C (Oct 2025 at $6B, GV-led), $250M Series D (Jan 2026 at $12B, Thrive + DST)
How it started
After selling Kensho to S&P Global, Daniel Nadler co-founded OpenEvidence in 2021 with Zachary Ziegler in Miami, betting doctors wanted a conversational interface grounded in the same journals and guidelines they already used — not the open internet.
What happened
The free, ad-supported platform grew through verification-based signups — around 65,000 new verified US clinicians a month at the July 2025 Series B — passed $100M annual revenue and 18M monthly clinical consultations by December 2025, and launched DeepConsult and a HIPAA-secure Dialer. It raised $210M in July 2025, $200M in October 2025, then $250M in January 2026.
How it ended up
Still scaling: the Series D funds multi-agent 'medical superintelligence' and compute, and Nadler bets focus beats OpenAI and Anthropic health side-hustles.
Background
OpenEvidence is a Miami-based startup founded in 2021 by Daniel Nadler, who previously sold Kensho to S&P Global, and Zachary Ziegler. Its product is an AI-powered medical search engine that answers doctors' clinical questions with citation-linked answers drawn from peer-reviewed journals and guidelines — free for verified clinicians and supported by advertising.
The bet was that doctors wanted a conversational interface grounded in the same literature they already trusted, not the open internet. Copyright-friendly licensing deals with the AMA, NEJM, JAMA Network's 13 journals, AAFP, ACEP and NCCN gave it gold-standard content and early trust.
Growth was explosive: by December 2025 the platform supported about 18 million clinical consultations a month, up from roughly 3 million a year earlier, was used daily by more than 40% of US physicians across 10,000+ hospitals, and had passed $100M in annual revenue. Exploding Topics lists OpenEvidence at +789% two-year search growth, a direct search-rising signal.
Investors responded: $210M Series B in July 2025 (GV, Kleiner), $200M Series C in October 2025 at $6B, and a $250M Series D in January 2026 co-led by Thrive Capital and DST at a $12B valuation, bringing total funding to about $700M. The capital funds a multi-agent 'medical superintelligence' architecture, with oncology cited as the first specialty.
What has to be true
- A free product removes adoption friction for time-poor doctors, and verification creates a trusted, exclusive distribution channel.
- Content licensing with the journals doctors already use made answers feel grounded, unlike general chatbots.
- Bottom-up habit beats top-down sales: Nadler builds for doctors rather than hospital CIOs, turning daily usage into the moat.
- Ad-supported economics with $100M+ revenue proved doctors as an audience monetize before big-ticket enterprise deals.
- The open risk is generalist competition: OpenAI's ChatGPT for Health and Anthropic's Claude for Healthcare target adjacent segments.
What can be applied
Give the highest-trust users the free product first: if doctors make it their daily default, valuation follows — but the moat depends on content partners and habit against well-funded generalists.
Aftermath
As of September 2026, OpenEvidence remains privately held and scaling. The January 2026 Series D at $12B — double its October valuation — funds training, compute and content-licensing partnerships for an agentic 'medical superintelligence' platform, with oncology models flagged as the first specialty. The company says it is adding doctors at tens of thousands per month and continues to sign gold-standard journal partnerships, positioning itself as the default operating system of medical knowledge in the US.
Sources
- OpenEvidence hits $12B valuation, with new round led by Thrive, DST
- OpenEvidence, An AI-Powered 'Brain Extender' For Doctors, Doubles Valuation To $12B With $250M Series D
- OpenEvidence clinches $250M series D as AI platform sees explosive growth with doctors
- 25 Top Startups (September 2026)
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