Tandem Diabetes Care, Inc.
MX ˙ BMV ˙ US8753722037
SecurityMX:TNDM / Tandem Diabetes Care, Inc.
InstitutionMillennium Management Llc
ManagerIsrael Englander
Latest Disclosed Ownership761,672 shares
Latest Disclosed Value $ 14,601,252
Millennium Management Llc ownership in TNDM / Tandem Diabetes Care, Inc.

On May 15, 2026 - Millennium Management Llc filed a 13F-HR form disclosing ownership of 761,672 shares of Tandem Diabetes Care, Inc. (MX:TNDM) valued at $14,601,252 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 583,573 shares of Tandem Diabetes Care, Inc.. This represents a change in shares of 30.52% during the quarter.

Millennium Management Llc has a history of taking positions in derivatives of the underlying security (TNDM) in the form of stock options. The firm currently holds call options representing 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

Upgrade to unlock premium data and export to Excel .

Institutional Put/Call Ratios
(Premium Subscription Required)

In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:TNDM / Tandem Diabetes Care, Inc. Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 761,672 178,099 30.52 14,601 13.84 0.0061
2026-02-17 2025-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 583,573 -122,329 -17.33 12,827 49.68 0.0054
2025-11-14 2025-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 705,902 -263,171 -27.16 8,570 -52.56 0.0037
2025-08-14 2025-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 969,073 741,488 325.81 18,064 314.29 0.0087
2025-05-15 2025-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 227,585 76,245 50.38 4,361 -20.01 0.0023
2025-02-14 2024-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 151,340 -1,283,316 -89.45 5,451 -91.04 0.0027
2024-11-14 2024-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 1,434,656 380,703 36.12 60,844 43.28 0.0289
2024-08-14 2024-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 1,053,953 28,999 2.83 42,464 17.00 0.0197
2024-05-15 2024-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 1,024,954 394,111 62.47 36,294 94.50 0.0155
2024-02-14 2023-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 630,843 126,974 25.20 18,660 78.31 0.0081
2023-11-14 2023-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 503,869 -543,516 -51.89 10,465 -59.28 0.0053
2023-08-14 2023-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 1,047,385 752,481 255.16 25,703 114.61 0.0127
2023-05-15 2023-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 294,904 -318,431 -51.92 11,976 -56.56 0.0069
2023-02-14 2022-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 613,335 540,252 739.23 27,569 688.36 0.0153
2022-11-14 2022-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 73,083 -20,298 -21.74 3,497 -36.73 0.0021
2022-08-15 2022-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 93,381 -362,711 -79.53 5,527 -89.58 0.0034
2022-05-16 2022-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 456,092 242,438 113.47 53,039 64.93 0.0281
2022-02-14 2021-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 213,654 44,192 26.08 32,159 58.97 0.0163
2021-11-15 2021-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 169,462 -132,950 -43.96 20,230 -31.32 0.0121
2021-08-16 2021-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 302,412 275,522 1,024.63 29,455 1,141.26 0.0181
2021-05-17 2021-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 26,890 -184,648 -87.29 2,373 -88.28 0.0017
2021-02-16 2020-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 211,538 -120,933 -36.37 20,240 -46.36 0.0146
2020-11-16 2020-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 332,471 -429,363 -56.36 37,735 -49.93 0.0465
2020-08-14 2020-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 761,834 761,834 75,361 0.1033
2020-05-14 2020-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 0 -357,720 -100.00 0 -100.00
2020-02-14 2019-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 357,720 -145,283 -28.88 21,324 -28.12 0.0267
2019-11-14 2019-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 503,003 -441,414 -46.74 29,667 -51.31 0.0469
2019-08-15 2019-06-30 13F/A-1 TANDEM DIABETES CARE COM NEW 875372203 944,417 112,792 13.56 60,934 15.39 0.0916
2019-08-14 2019-06-30 13F CNH INDL N V SHS 875372203 2,071,437 1,239,812 21,294
2019-05-14 2019-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 831,625 177,936 27.22 52,808 112.76 0.0790
2019-02-15 2018-12-31 13F/A-1 TANDEM DIABETES CARE COM NEW 875372203 653,689 -107,311 -14.10 24,821 -23.86 0.0387
2019-02-14 2018-12-31 13F TANDEM DIABETES CARE COM NEW 875372203 653,689 24,821
2018-11-14 2018-09-30 13F TANDEM DIABETES CARE COM NEW 875372203 761,000 15,559 2.09 32,601 98.60 0.0400
2018-08-14 2018-06-30 13F TANDEM DIABETES CARE COM NEW 875372203 745,441 -106,345 -12.48 16,415 288.52 0.0214
2018-05-15 2018-03-31 13F TANDEM DIABETES CARE COM NEW 875372203 851,786 851,786 4,225 0.0056
2017-11-14 2017-09-30 13F TANDEM DIABETES CARE COM 875372104 0 -101,939 -100.00 0 -100.00
2017-08-14 2017-06-30 13F TANDEM DIABETES CARE COM 875372104 101,939 -33,208 -24.57 82 -49.38 0.0001
2017-05-15 2017-03-31 13F TANDEM DIABETES CARE COM 875372104 135,147 135,147 162 0.0003
2017-02-14 2016-12-31 13F TANDEM DIABETES CARE COM 875372104 0 -820,309 -100.00 0 -100.00
2016-11-14 2016-09-30 13F TANDEM DIABETES CARE COM 875372104 820,309 -66,687 -7.52 6,284 -6.04 0.0105
2016-08-15 2016-06-30 13F TANDEM DIABETES CARE COM 875372104 886,996 240,651 37.23 6,688 18.79 0.0153
2016-05-16 2016-03-31 13F TANDEM DIABETES CARE COM 875372104 646,345 197,317 43.94 5,630 6.17 0.0141
2016-02-16 2015-12-31 13F TANDEM DIABETES CARE COM 875372104 449,028 -165,780 -26.96 5,303 -2.09 0.0111
2015-11-16 2015-09-30 13F TANDEM DIABETES CARE COM 875372104 614,808 -228,985 -27.14 5,416 -40.79 0.0105
2015-08-14 2015-06-30 13F TANDEM DIABETES CARE COM 875372104 843,793 -119,162 -12.37 9,147 -24.73 0.0173
2015-05-15 2015-03-31 13F TANDEM DIABETES CARE COM 875372104 962,955 596,789 162.98 12,152 161.33 0.0226
2015-02-17 2014-12-31 13F TANDEM DIABETES CARE COM 875372104 366,166 38,488 11.75 4,650 5.75 0.0099
2014-11-14 2014-09-30 13F TANDEM DIABETES CARE COM 875372104 327,678 -79,820 -19.59 4,397 -33.64 0.0111
2014-08-14 2014-06-30 13F TANDEM DIABETES CARE COM 875372104 407,498 -6,886 -1.66 6,626 -27.62 0.0184
2014-05-15 2014-03-31 13F TANDEM DIABETES CARE COM 875372104 414,384 163,195 64.97 9,154 41.42 0.0265
2014-02-14 2013-12-31 13F TANDEM DIABETES CARE COM 875372104 251,189 251,189 6,473 0.0204
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2025-05-15 2025-03-31 13F TANDEM DIABETES CARE COM NEW Call 0 -100.00 0 -100.00 n/a n/a n/a
2025-02-14 2024-12-31 13F TANDEM DIABETES CARE COM NEW Call 10,000 0.00 360 -15.09 n/a n/a n/a
2024-11-14 2024-09-30 13F TANDEM DIABETES CARE COM NEW Call 10,000 -75.00 424 -73.68 n/a n/a n/a
2024-08-14 2024-06-30 13F TANDEM DIABETES CARE COM NEW Call 40,000 1,612 n/a n/a n/a
2024-02-14 2023-12-31 13F TANDEM DIABETES CARE COM NEW Call 0 -100.00 0 -100.00 n/a n/a n/a
2023-11-14 2023-09-30 13F TANDEM DIABETES CARE COM NEW Call 80,000 300.00 1,662 238.98 n/a n/a n/a
2023-08-14 2023-06-30 13F TANDEM DIABETES CARE COM NEW Call 20,000 491 n/a n/a n/a
2022-02-14 2021-12-31 13F TANDEM DIABETES CARE COM NEW Call 0 -100.00 0 -100.00 n/a n/a n/a
2021-11-15 2021-09-30 13F TANDEM DIABETES CARE COM NEW Call 10,000 0.00 1,194 22.59 n/a n/a n/a
2021-08-16 2021-06-30 13F TANDEM DIABETES CARE COM NEW Call 10,000 -50.00 974 -44.82 n/a n/a n/a
2021-05-17 2021-03-31 13F TANDEM DIABETES CARE COM NEW Call 20,000 100.00 1,765 84.43 n/a n/a n/a
2021-02-16 2020-12-31 13F TANDEM DIABETES CARE COM NEW Call 10,000 957 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2025-02-14 2024-12-31 13F TANDEM DIABETES CARE COM NEW Put 0 -100.00 0 -100.00 n/a n/a n/a
2024-11-14 2024-09-30 13F TANDEM DIABETES CARE COM NEW Put 30,000 -57.14 1,272 -54.89 n/a n/a n/a
2024-08-14 2024-06-30 13F TANDEM DIABETES CARE COM NEW Put 70,000 133.33 2,820 165.54 n/a n/a n/a
2024-05-15 2024-03-31 13F TANDEM DIABETES CARE COM NEW Put 30,000 200.00 1,062 260.00 n/a n/a n/a
2024-02-14 2023-12-31 13F TANDEM DIABETES CARE COM NEW Put 10,000 296 n/a n/a n/a
2023-11-14 2023-09-30 13F TANDEM DIABETES CARE COM NEW Put 0 -100.00 0 -100.00 n/a n/a n/a
2023-08-14 2023-06-30 13F TANDEM DIABETES CARE COM NEW Put 20,000 491 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.