Ownership Submission
FORM 3
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Vosseller Leigh
2. Date of Event Requiring Statement (Month/Day/Year)
01/01/2018
3. Issuer Name and Ticker or Trading Symbol
TANDEM DIABETES CARE INC [TNDM]
(Last)
(First)
(Middle)
C/O TANDEM DIABETES CARE, INC., 11075 ROSELLE STREET
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Senior Vice President and CFO
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

SAN DIEGO, CA 92121
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)
2. Amount of Securities Beneficially Owned
(Instr. 4)
3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)
4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 754
D
 
Common Stock 145
I
See footnote (1)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)
2. Date Exercisable and Expiration Date
(Month/Day/Year)
3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)
4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)
6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (2)   (3)   (4) Common Stock 8,056 (5) $ 67.694 (5) D  
Stock Option (6)   (7)   (4) Common Stock 5,799 (5) $ 150 (5) D  
Stock Option (6)   (8)   (4) Common Stock 2,711 (5) $ 119.2 (5) D  
Stock Option (6)   (9)   (4) Common Stock 3,390 (5) $ 69.5 (5) D  
Stock Option (6)   (10)   (4) Common Stock 6,780 (5) $ 23 (5) D  
Stock Option (6)   (11)   (4) Common Stock 7,500 (5) $ 9 (5) D  
Stock Option (6)   (12)   (4) Common Stock 80,000 (5) $ 2.59 (5) D  

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Vosseller Leigh
C/O TANDEM DIABETES CARE, INC.
11075 ROSELLE STREET
SAN DIEGO, CA 92121
      Senior Vice President and CFO  

Signatures

/s/ David B. Berger, Attorney-in-Fact for Leigh Vosseller 01/02/2018
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The securities are held by the Leigh A. Vosseller Trust dated January 17, 2010, of which Leigh Vosseller is the Trustee.
(2) Granted pursuant to the Tandem Diabetes Care, Inc. 2006 Stock Incentive Plan.
(3) The date of grant of the option was 09/23/2013. All shares subject to the option have vested.
(4) The expiration date for these options is 10 years from the date of grant.
(5) Reflects a 1-for-10 reverse stock split of the issued and outstanding shares of common stock, which was effective 10/09/2017.
(6) Granted pursuant to the Tandem Diabetes Care, Inc. 2013 Stock Incentive Plan.
(7) The date of grant of the option was 11/13/2013. All shares subject to the option have vested.
(8) The date of grant of the option was 05/21/2015. 25% of the shares subject to the option vested on 05/21/2016 and the remainder vests in 36 equal monthly installments thereafter.
(9) The date of grant of the option was 02/16/2016. 25% of the shares subject to the option vested on 02/16/2017 and the remainder vests in 36 equal monthly installments thereafter.
(10) The date of grant of the option was 12/16/2016. 50% of the shares subject to the option vested on 12/16/2017 and the remainder vests in 12 equal monthly installments thereafter.
(11) The date of grant of the option was 05/17/2017. All shares subject to the option will vest 25% on 05/17/2018 and the remainder vests in 36 equal monthly installments thereafter.
(12) The date of grant of the option was 12/01/2017. All shares subject to the option will vest 50% on 12/01/2018 and the remainder vests in 12 equal monthly installments thereafter.
 
Remarks:
Exhibit 24.1 - Power of Attorney

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