Institutional HoldersBeta

Who holds a company, from every 13F filed for the quarter, one row per filer exactly as filed, against the latest share count the company reported.

TANDEM DIABETES CARE INC

CIK 0001438133TNDM· quarter ending 2026-06-30

Shares outstanding

69,578,707

as of 2026-08-03 · 10-Q cover page, filed 2026-08-06

Held by 13F filers

313,658,000

selection includes debt or preferreds — no % of shares outstanding

Holders

+15 vs 2026-03-31 · 18 new, 3 exited

Value

$298.8M

shares -1.1% vs prior quarter

13F holdings exceed the share count. This is normal for heavily shorted stocks: shares lent to short sellers are reported by the lender and again by whoever bought them. Related filers occasionally report the same position twice as well.

Share classes (cover page of the 10-Q filed 2026-08-06, as of 2026-08-03)

Class	Listed	Shares outstanding	Held by 13F filers	% of class	Holders	CUSIP
Common stock	TNDM · NASDAQ	69,578,707	78,798,150	113.3%	274	875372203

Each class is compared with its own share count; classes are not added together. A class that is not exchange-listed cannot be held by 13F filers.

Securities (CUSIPs held in 13F this quarter)

tick to combine

Count	CUSIP	Class (as filers write it)	Holders	Shares held	Class shares	% of class	Value	Options	Mapped via
	875372203	COM NEW	274	78,798,150	69,578,707	113.3%	$1.2B	7 call / 7 put	13DG	holders →
	875372AD6	NOTE 1.500% 3/1not common	29	250,000 $313.4M principal	—	—	$298.8M	—	NPORT	holders →

Totals combine the ticked CUSIPs and update as you tick: common-stock classes by default; preferreds, notes, warrants and depositary shares are listed but not counted. "holders →" shows a single CUSIP on its own. Bonds are held as a principal amount, not shares. Options positions are never counted as holdings. 3 further CUSIPs map to this company (mostly bonds) but no 13F filer held them this quarter.

Top holders (29 of 29 · 875372AD6)

change vs 2026-03-31

#	Filer	Shares / principal	% of class	Value	Change
1	Linden Advisors LP	74,791,000	—	$71.2M	+20,000,000 (+36.5%)
2	BANK OF MONTREAL /CAN/	42,039,000	—	$40.0M	—
3	Opti Capital Management, LP	27,500,000	—	$26.4M	NEW
4	Balyasny Asset Management L.P.	25,000,000	—	$23.9M	NEW
5	Context Capital Management, LLC	20,000,000	—	$19.0M	-18,500,000 (-48.1%)
6	Empyrean Capital Partners, LP	18,500,000	—	$17.7M	NEW
7	DeepCurrents Investment Group LLC	17,804,000	—	$16.9M	-1,500,000 (-7.8%)
8	Fort Baker Capital Management LP	15,000,000	—	$14.4M	NEW
9	GOLDMAN SACHS GROUP INC	10,443,000	—	$9.9M	NEW
10	Calamos Advisors LLC	8,550,000	—	$8.2M	—
11	Jump Financial, LLC	8,312,000	—	$7.9M	NEW
12	BlackRock, Inc.	7,025,000	—	$6.6M	+1,875,000 (+36.4%)
13	ADVENT CAPITAL MANAGEMENT /DE/	6,196,000	—	$5.9M	NEW
14	ARISTEIA CAPITAL, L.L.C.	6,000,000	—	$5.7M	-4,000,000 (-40.0%)
15	CITIGROUP INC	5,263,000	—	$5.0M	+5,108,000 (+3295.5%)
16	FMR LLC	3,786,000	—	$3.6M	-25,000 (-0.7%)
17	Walleye Capital LLC	3,500,000	—	$3.3M	NEW
18	LAZARD ASSET MANAGEMENT LLC	2,533,000	—	$24K	-5,926,000 (-70.1%)
19	TENOR CAPITAL MANAGEMENT Co., L.P.	2,500,000	—	$2.4M	NEW
20	CAPSTONE INVESTMENT ADVISORS, LLC	2,500,000	—	$2.4M	NEW
21	ZAZOVE ASSOCIATES LLC	2,500,000	—	$2.4M	NEW
22	CSS LLC/IL	2,500,000	—	$2.4M	NEW
23	Jefferies Financial Group Inc.	1,100,000	—	$1.0M	NEW
24	Bank of New York Mellon Corp	250,000	—	$238K	NEW
25	SG Americas Securities, LLC	25,000	—	$2.4M	NEW
26	INSIGNEO ADVISORY SERVICES, LLC	17,000	—	$16K	NEW
27	WEALTH ENHANCEMENT ADVISORY SERVICES, LLC	15,000	—	$14K	NEW
28	ROYAL BANK OF CANADA	7,000	—	$7K	NEW
29	BNP PARIBAS FINANCIAL MARKETS	2,000	—	$2K	-1,023,000 (-99.8%)

Exited since 2026-03-31 (3 filers; largest 3 shown)

VOYA INVESTMENT MANAGEMENT LLC	−117,415,000
Point72 Asset Management, L.P.	−7,500,000
JANE STREET GROUP, LLC	−292,000

Large holders from 13D/13G (latest per reporting person, last 2 years)

Filed when a holder crosses 5% or changes materially, so often more current than the quarter-end 13F. Percentages are the filer's own, against the share count they used.

Reporting person	Form	Filed	Event	Shares	% of class
Voya Financial, Inc.	SCHEDULE 13G/A	2026-08-06	2026-06-30	149,088	0.2%
Vanguard Capital Management	SCHEDULE 13G	2026-04-30	2026-03-31	3,553,772	5.18%
Vanguard Portfolio Management	SCHEDULE 13G	2026-04-29	2026-03-31	4,052,274	5.91%
The Vanguard Group	SCHEDULE 13G/A	2026-03-27	2026-03-13	0	0%
ArrowMark Colorado Holdings, LLC	SCHEDULE 13G/A	2026-02-17	2025-12-31	2,889,691	4.26%
John Petry	SCHEDULE 13G	2025-05-15	2025-03-31	4,466,307	6.71%
Sessa Capital GP, LLC	SCHEDULE 13G	2025-05-15	2025-03-31	4,466,307	6.71%
Sessa Capital IM GP, LLC	SCHEDULE 13G	2025-05-15	2025-03-31	4,466,307	6.71%
Sessa Capital IM, L.P.	SCHEDULE 13G	2025-05-15	2025-03-31	4,466,307	6.71%
Sessa Capital (Master), L.P.	SCHEDULE 13G	2025-05-15	2025-03-31	4,466,307	6.71%
BlackRock, Inc.	SCHEDULE 13G/A	2025-04-29	2025-03-31	10,106,682	15.2%

Source: SEC Form 13F-HR information tables for the quarter ending 2026-06-30 (filed within 45 days of quarter end; amendments applied; values normalised to dollars), the share count from the company's latest 10-K/10-Q XBRL cover page, and Schedule 13D/13G filings. Each row is a legal 13F filer as filed — related entities (e.g. Vanguard's advisers) are not merged. Retail brokerage accounts are not reported on 13F, so the remainder is mostly retail and insiders.