Stocks › TNDM

Tandem Diabetes Care TNDM

US equityMarket cap rank #3170

$15.84 −$0.32 (-1.98%)

Pre-market · Oct 8, 7:00 am ET · After hours $15.80 -0.25%

Open$15.80

Prev close$16.16

Day range$15.73 – $16.64

Volume2.27M

Market cap$1.10B

P/E (TTM)–

Dividend yield–

Ownership & positioning

Who holds it, who is betting against it, and where the big money is moving

Institutional ownership116.0%-0.81 pts vs. prior quarter

Institutions holding333-2 vs. prior quarter

Insider trades (recent)36 buys / 14 sellsNet buying

Short interest17.93% of floatDays to cover 7.9 · as of 15 Sep 2026

Short-sale volume share20.4%5-day average of daily volume

Short-sale volume as % of daily volume

Large-order net flow, last 20 sessions

Net of large-order buying minus selling, in USD. Over this window: −$1.83M (10 inflow days, 10 outflow days).

Net flow by order size, last 20 sessions

Super/Big orders approximate institutional-size trades; Mid/Small approximate retail-size trades. Net buy minus sell value in each bucket, summed over the window.

The five largest holders on file together own 40.2% of shares outstanding.

Largest holders

BlackRock16.65%
Sessa Capital IM, L.P.7.33%
Vanguard Portfolio Management, LLC6.18%
Vanguard Capital Management, LLC5.16%
First Light Asset Management, LLC4.86%
State Street Global Advisors4.10%
GW&K Investment Management, LLC3.69%
Jennison Associates LLC3.35%

By investor type

Mutual Fund80.31%
Hedge Fund27.38%
Public Company4.04%
Sovereign Wealth Fund1.42%
Government Pension Fund1.40%
Private Company1.06%
Individual/Insider1.00%
Insurance Company0.29%

Reported short interest has fallen from 18.58% to 17.93% of float over the last 6 biweekly reports (30 Jun 2026 to 15 Sep 2026).

Recent institutional activity

Holder	Type	Period	Share change	New stake
First Light Asset Management, LLC	Mutual Fund	2026/Q3	+2,068,838	4.9%
Woodline Partners LP	Hedge Fund	2026/Q3	+1,307,439	1.9%
BlackRock	Mutual Fund	2026/Q3	+892,281	16.6%
Jennison Associates LLC	Mutual Fund	2026/Q3	+672,981	3.4%
Qube Research & Technologies Ltd	Mutual Fund	2026/Q3	+631,862	1.0%
Verition Fund Management LLC	Hedge Fund	2026/Q3	+592,881	1.0%
Millennium Management LLC	Hedge Fund	2026/Q3	+550,067	1.9%
Freestone Grove Partners LP	Hedge Fund	2026/Q3	+535,392	2.7%
BMO Asset Management	Mutual Fund	2026/Q3	+527,531	0.8%
Jacobs Levy Equity Management Inc	Mutual Fund	2026/Q3	+482,483	2.9%
Arrowstreet Capital, Limited Partnership	Mutual Fund	2026/Q3	+474,133	1.0%
Leap Investments LP	Mutual Fund	2026/Q3	+397,600	0.6%
Sessa Capital IM, L.P.	Hedge Fund	2026/Q3	+369,243	7.3%
Alberta Investment Management Corporation	Government Pension Fund	2026/Q3	+313,700	0.5%
Vanguard Portfolio Management, LLC	Mutual Fund	2026/Q3	+306,334	6.2%

Institutional buy/sell activity by reporting period, largest moves first.

Insider transactions

Date	Insider	Title	Transaction	Shares	Price	Held after
16 Sep 2026	Mark Novara	Executive Vice President	Intent to Sell (Form 144)	-360	$17.53	–
17 Aug 2026	Mark Novara	Executive Vice President	Intent to Sell (Form 144)	-131	$22.26	–
14 Aug 2026	Jean-Claude Kyrillos	Chief Operating Officer	Derivative Exercise and Sale	-535	$22.72	30,290
14 Aug 2026	Jean-Claude Kyrillos	Chief Operating Officer	Derivative Exercise and Retained	+475	–	30,290
14 Aug 2026	Shannon Hansen	Chief Legal, Privacy & Compliance Officer and Secretary	Derivative Exercise and Sale	-1,535	$22.72	33,585
14 Aug 2026	Shannon Hansen	Chief Legal, Privacy & Compliance Officer and Secretary	Derivative Exercise and Retained	+1,479	–	33,585
14 Aug 2026	John Sheridan	Chief Executive Officer	Derivative Exercise and Sale	-8,099	$22.72	160,260
14 Aug 2026	John Sheridan	Chief Executive Officer	Derivative Exercise and Retained	+7,817	–	160,260
14 Aug 2026	Leigh Vosseller	Chief Financial Officer	Derivative Exercise and Sale	-1,479	$22.72	77,620
14 Aug 2026	Leigh Vosseller	Chief Financial Officer	Derivative Exercise and Retained	+2,641	–	77,620
14 Aug 2026	Rick Carpenter	Chief Technology Officer	Derivative Exercise and Sale	-1,277	$22.72	32,148
14 Aug 2026	Rick Carpenter	Chief Technology Officer	Derivative Exercise and Retained	+1,230	–	32,148
14 Aug 2026	Susan Morrison	Executive Vice President	Derivative Exercise and Sale	-809	$22.72	52,788
14 Aug 2026	Susan Morrison	Executive Vice President	Derivative Exercise and Retained	+2,018	–	52,788
14 Aug 2026	Elizabeth Gasser	Chief Strategy Officer	Derivative Exercise and Sale	-1,618	$22.72	34,505
14 Aug 2026	Elizabeth Gasser	Chief Strategy Officer	Derivative Exercise and Retained	+1,396	–	34,505
14 Jul 2026	Jean-Claude Kyrillos	Chief Operating Officer	Derivative Exercise and Sale	-1,926	$15.28	29,815
14 Jul 2026	Jean-Claude Kyrillos	Chief Operating Officer	Derivative Exercise and Retained	+1,710	–	29,815
16 Jun 2026	Mark Novara	Executive Vice President	Intent to Sell (Form 144)	-361	$16.69	–
1 Jun 2026	Elizabeth Gasser	Chief Strategy Officer	Other Acquisition	+7,160	–	33,109

From Form 4/Form 144 filings. Negative share counts are disposals (sales, gifts, or shares withheld for taxes); positive are acquisitions.

Short interest, by report

Report date	Shares short	% of float	Days to cover
15 Sep 2026	12,474,385	17.9%	7.9
31 Aug 2026	11,753,819	16.9%	8.2
14 Aug 2026	10,585,732	15.2%	3.9
31 Jul 2026	11,242,544	16.4%	6.6
15 Jul 2026	13,115,208	19.1%	8.7
30 Jun 2026	12,731,073	18.6%	5.6

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