Tandem Diabetes Care, Inc. (TNDM) Ownership
TNDM ownership summary
as of October 18, 2026- Institutions
- 115.6% of shares outstanding
- Insiders
- 1.17% of shares outstanding
- Shares outstanding
- 69.6M
- Float
- 63.8M shares available to trade
- Short interest
- 25.73% 13.4M shares short
- Days to cover
- 6.36 short interest up 7.2% vs prior month
- Institutions 115.57%
- Insiders 1.17%
TNDM top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | BlackRock Inc | 16.65% | 11.6M | $188.1M | +892,281 (+8.3%) | June 30, 2026 |
| 2 | Sessa Capital, L.P | 7.33% | 5.1M | $82.8M | +369,243 (+7.8%) | June 30, 2026 |
| 3 | Vanguard Portfolio Management, LLC | 6.18% | 4.3M | $69.8M | +306,334 (+7.7%) | June 30, 2026 |
| 4 | First Light Asset Management, LLC | 4.86% | 3.4M | $54.9M | +2.1M (+157.4%) | June 30, 2026 |
| 5 | Vanguard Capital Management, LLC | 4.45% | 3.1M | $50.3M | +57,617 (+1.9%) | June 30, 2026 |
| 6 | State Street Corp | 4.10% | 2.9M | $46.3M | +189,386 (+7.1%) | June 30, 2026 |
| 7 | GW&K Investment Management, LLC | 3.69% | 2.6M | $41.7M | −120,074 (−4.5%) | June 30, 2026 |
| 8 | Jennison Associates LLC | 3.35% | 2.3M | $37.9M | +672,981 (+40.6%) | June 30, 2026 |
| 9 | Paradice Investment Management LLC | 2.91% | 2.0M | $32.9M | −18,411 (−0.9%) | June 30, 2026 |
| 10 | Jacobs Levy Equity Management, Inc. | 2.88% | 2.0M | $32.6M | +482,483 (+31.7%) | June 30, 2026 |
| 11 | Freestone Grove Partners LP | 2.68% | 1.9M | $30.3M | +535,392 (+40.2%) | June 30, 2026 |
| 12 | Geode Capital Management, LLC | 2.59% | 1.8M | $29.2M | +120,934 (+7.2%) | June 30, 2026 |
| 13 | Driehaus Capital Management LLC | 2.57% | 1.8M | $29.0M | −517,418 (−22.5%) | June 30, 2026 |
| 14 | Citadel Advisors Llc | 2.49% | 1.7M | $28.2M | −456,788 (−20.8%) | June 30, 2026 |
| 15 | Millennium Management LLC | 1.89% | 1.3M | $21.3M | +550,067 (+72.2%) | June 30, 2026 |
| 16 | Woodline Partners LP | 1.88% | 1.3M | $21.2M | +1.3M (0.0%) | June 30, 2026 |
| 17 | ArrowMark Colorado Holdings, LLC (ArrowMark Partners) | 1.87% | 1.3M | $21.1M | −1.8M (−58.1%) | June 30, 2026 |
| 18 | UBS Group AG | 1.65% | 1.1M | $18.6M | −901,221 (−44.0%) | June 30, 2026 |
| 19 | FMR Inc | 1.40% | 976K | $15.9M | +262,421 (+36.8%) | June 30, 2026 |
| 20 | Royce & Associates, LP | 1.29% | 901K | $14.6M | +204,000 (+29.3%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 14 holders added 8.0M shares and 6 cut 3.8M.
TNDM top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | iShares Core S&P Small-Cap ETF | 5.95% | 4.1M | $67.2M | +1,068 (+0.0%) | September 30, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 3.14% | 2.2M | $35.5M | — | August 31, 2026 |
| 3 | iShares Russell 2000 ETF | 2.59% | 1.8M | $29.3M | −20,800 (−1.1%) | September 30, 2026 |
| 4 | Vanguard Small Cap Index | 2.25% | 1.6M | $25.4M | −8,516 (−0.5%) | September 30, 2026 |
| 5 | Vanguard MStar Small Cap Growth Indx Inv | 1.25% | 872K | $14.2M | −30,388 (−3.4%) | September 30, 2026 |
| 6 | Fidelity Enhanced Small Cap Core ETF | 1.13% | 789K | $12.8M | +1,656 (+0.2%) | September 30, 2026 |
| 7 | PGIM Jennison Health Sciences Z | 1.12% | 778K | $12.6M | +97,478 (+14.3%) | September 30, 2026 |
| 8 | Fidelity Small Cap Index | 1.10% | 763K | $12.4M | +6,295 (+0.8%) | July 31, 2026 |
| 9 | iShares Russell 2000 Growth ETF | 0.94% | 654K | $10.6M | −827 (−0.1%) | September 30, 2026 |
| 10 | State Street SPDR Port S&P 600 Sm CpETF | 0.91% | 634K | $10.3M | — | September 30, 2026 |
| 11 | Meridian Growth Legacy | 0.69% | 483K | $7.8M | −13,470 (−2.7%) | June 30, 2026 |
| 12 | Heptagon Driehaus US Micro Cap Eq C$ Acc | 0.68% | 471K | $7.7M | — | August 31, 2026 |
| 13 | Strategic Advisers Fidelity US TtlStk | 0.67% | 466K | $7.6M | −87,800 (−15.9%) | August 31, 2026 |
| 14 | Royce Small-Cap Opportunity Invmt | 0.62% | 434K | $7.1M | +10,716 (+2.5%) | September 30, 2026 |
| 15 | FTGF RY US SmCp Opp A USD Dis(A) | 0.62% | 433K | $7.0M | −12,545 (−2.8%) | August 31, 2026 |
| 16 | Vanguard Russell 2000 ETF | 0.58% | 406K | $6.6M | +4,578 (+1.1%) | September 30, 2026 |
| 17 | Schwab US Small-Cap ETF™ | 0.53% | 369K | $6.0M | +243 (+0.1%) | September 30, 2026 |
| 18 | iShares S&P Small-Cap 600 Growth ETF | 0.51% | 357K | $5.8M | — | September 30, 2026 |
| 19 | iShares US Medical Devices ETF | 0.49% | 342K | $5.5M | +5,976 (+1.8%) | September 30, 2026 |
| 20 | Fidelity Extended Market Index | 0.48% | 335K | $5.4M | −4,718 (−1.4%) | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
TNDM insider transactions
latest 6| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-03-17 | Mark David Novara | Sell | $23.05 | 187 | $4,310 |
| 2026-03-05 | Mark David Novara | Sell | $22.81 | 2 | $46 |
| 2026-03-03 | Gilbert Ray Cisneros, Jr. | Buy | $23.74 | — | — |
| 2025-09-22 | Josh Gottheimer | Buy | $13.06 | — | — |
| 2025-08-11 | John F Sheridan | Buy | $10.23 | 10,000 | $102,300 |
| 2025-08-08 | Leigh Vosseller | Buy | $10.89 | 13,720 | $149,411 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
TNDM shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns TNDM
Institutional investors own 115.6% of Tandem Diabetes Care's shares and insiders 1.17%. The largest holder is BlackRock Inc with 16.65% of the shares (11.6M), as of June 30, 2026. Among the top 20 institutions, 14 added shares and 6 reduced their stake in the latest filings. Short interest is 25.73% of the float, or 6.36 days of average trading volume. The share count rose 188.5% since 2014.
Related: TNDM analyst forecast, TNDM key metrics. See the TNDM stock overview for the latest quote and news.
TNDM ownership FAQ
Who owns the most Tandem Diabetes Care stock?
The largest shareholders of Tandem Diabetes Care are BlackRock Inc (16.65%), Sessa Capital, L.P (7.33%), Vanguard Portfolio Management, LLC (6.18%), First Light Asset Management, LLC (4.86%), Vanguard Capital Management, LLC (4.45%).
What percentage of Tandem Diabetes Care is owned by institutions?
Institutions hold 115.6% of Tandem Diabetes Care's shares outstanding; insiders hold 1.17%.
Which funds own Tandem Diabetes Care?
The largest fund holders of Tandem Diabetes Care are iShares Core S&P Small-Cap ETF (5.95%), Vanguard MStar Total Stk Mkt Idx Invest (3.14%), iShares Russell 2000 ETF (2.59%), Vanguard Small Cap Index (2.25%), Vanguard MStar Small Cap Growth Indx Inv (1.25%).
What is Tandem Diabetes Care's short interest?
13.4M shares of Tandem Diabetes Care were sold short, 25.73% of the float; at the average daily volume it would take 6.36 days to cover.
Are insiders buying or selling Tandem Diabetes Care?
Of the latest 6 reported insider transactions in Tandem Diabetes Care (since August 8, 2025), 4 were purchases and 2 were sales.
How many shares of Tandem Diabetes Care are outstanding?
Tandem Diabetes Care has 69.6M shares outstanding, of which 63.8M are in the public float.