Tandem Diabetes Care, Inc.
Tandem Diabetes Care, Inc. (TNDM) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · TNDM · as of Sep 30, 2025
Ownership Breakdown
270
Institutional Holders
▼ 14 vs Q2
$911.35M
Total Inst. Value
▼ $596.00M vs Q2
68.53M
Shares Outstanding
freeFloat 91.82%
75.08M
13F Shares Held
▼ 5.91M vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
TNDM largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
BLACKROCK, INC. surgical & medical instruments & apparatus | 12.10M | 18.05% | 18.05% | $146.91B | Nov 12, 2025 | ▲ 1.23M |
VANGUARD GROUP INC surgical & medical instruments & apparatus | 7.06M | 10.53% | 10.53% | $85.75B | Nov 7, 2025 | ▼ 306.5K |
SESSA CAPITAL IM, L.P. surgical & medical instruments & apparatus | 5.00M | 7.46% | 7.46% | $60.70B | Nov 14, 2025 | — held |
ARROWMARK COLORADO HOLDINGS LLC surgical & medical instruments & apparatus | 3.69M | 5.51% | 5.51% | $44.81B | Nov 14, 2025 | ▲ 991.6K |
UBS GROUP AG surgical & medical instruments & apparatus | 2.75M | 4.09% | 4.09% | $33.33B | Nov 13, 2025 | — held |
GW&K INVESTMENT MANAGEMENT, LLC surgical & medical instruments & apparatus | 2.72M | 4.06% | 4.06% | $33.04B | Nov 12, 2025 | ▼ 168.5K |
STATE STREET CORP surgical & medical instruments & apparatus | 2.67M | 3.98% | 3.98% | $32.39B | Nov 14, 2025 | ▲ 22.3K |
HOOD RIVER CAPITAL MANAGEMENT LLC surgical & medical instruments & apparatus | 2.55M | 3.81% | 3.81% | $30.98B | Nov 14, 2025 | ▼ 13.3K |
PARADICE INVESTMENT MANAGEMENT LLC surgical & medical instruments & apparatus | 2.20M | 3.28% | 3.28% | $26.67B | Oct 20, 2025 | ▲ 429.3K |
FREESTONE GROVE PARTNERS LP surgical & medical instruments & apparatus | 1.87M | 2.79% | 2.79% | $22.71B | Nov 14, 2025 | NEW |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
22
Increased
+6.34M shares4
New Positions
first time holders22
Decreased
−3.44M shares0
Sold Out
fully exitedNet shares change (top 50)
+2.90M
+6.34M / −3.44M
Net new holders
+4
4 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
TNDM insider trading · insider activity
Source: SEC Form 4
54
Buy transactions
53
Sell transactions
1.02
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Gasser Elizabeth Anne EVP, Chief Strategy Officer | Jun 2, 2026 | Gift | 7,160 | — | — | 33.1K | Form 4 ↗ |
Gasser Elizabeth Anne EVP, Chief Strategy Officer | Jun 2, 2026 | Gift | 7,160 | — | — | 0 | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Tandem Diabetes Care, Inc. (TNDM) is primarily owned by institutional investors, who hold approximately 100.0% of total shares outstanding. Company insiders own approximately 8.18%, while retail and public investors account for the remaining 0.00%.
The largest institutional shareholder of Tandem Diabetes Care, Inc. is BLACKROCK, INC., holding approximately 12.10 million shares — equal to 18.05% of outstanding shares — as of September 30, 2025.
A total of 270 institutional investors currently hold TNDM stock, with a combined institutional value of approximately $911,349,852 as of the most recent 13F filing period.
Frequently asked questions
TNDM ownershipTandem Diabetes Care, Inc. (TNDM) is primarily owned by institutional investors, who hold approximately 100.0% of shares. The largest shareholder is BLACKROCK, INC. with a 18.05% stake. Company insiders hold 8.18%. Data sourced from SEC Form 13F as of September 30, 2025.