SecProbe.io

October 29, 2013
Via E -mail
Kim D. Blickenstaff
President and Chief Executive Officer
Tandem Diabetes Care, Inc.
11045 Roselle Street
San Diego, CA  92121

Re: Tandem Diabetes Care, Inc.
Amendment No. 1 to Registration Statement on Form S-1
Filed  October  24, 2013
  File No. 333 -191601

Dear Mr. Blickenstaff :

We have reviewed your registration statement  and have the following comments.  In
some of our comments, we may ask you to provide us with information so we may better
understand your disclo sure.

Please respond to this letter by amending your registration statement and providing the
requested information.   Where you do not believe our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us  why in your
response.

After reviewing any amendment to your registration statement and the information you
provide in response to these comments, we may have additional comments.

Critical Accounting Policies and Management Estimates and Assumptions

Stock  Based Compensation, pages 60 -65

1. We note your October 24, 2013 response to comment 23 issued in our letter dated
September 6, 2013 .  Please revise to disclose the reason for the significant differences
between your estimated IPO price and the estimated fair value of your stock, similar to
the information provided in your response.  Your disclosure should indicate how you
determined the scenario probability weighting for “early IPO ,” “late IPO ,” and “non -
IPO” in the September 30, 2013 valuation,  considering the progress with your offering.
Please also discuss the significant differences in the methodologies and assumptions that
were used to estimate the IPO price with the methodologies and assumptions used in the
valuation at September 30, 2013.

Kim D. Blickenstaff
Tandem Diabetes Care, Inc.
October 29, 2013
Page 2

 Exclusive Forum, page 119

2. We note your revised  disclosure concerning forum selection.  Several lawsuits are
currently challenging the validity of choice of forum provisions in certificates of
incorporation.  Please disclose that although you have in cluded a choice of forum clause
in your amended and restated certification of incorporation, it is possible that a court
could rule that such provision is inapplicable or unenforceable.

We urge all persons who are responsible for the accuracy and adequacy of the disclosure
in the filing to be certain that the filing includes the information the Securities Act of 1933 and
all applicable Securities Act rules require.   Since the company and its management are in
possession of all facts relating to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosures they have made.

Notwithstanding our comments, in the event you request acceleration of the effective date
of the pending registration statement please provide a written statement from the company
acknowledging that:

 should the Commission or the staff, acting pursuant to delegated authority, declare the
filing effective, it does not foreclose the Commissi on from taking any action with respect
to the filing;

 the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and acc uracy of the disclosure in the filing; and

 the company may not assert staff comments and the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal
securities laws of the United States.

Please refer to Rules 460 and 461 regarding requests for acceleration.  We will consider a
written request for acceleration of the effective date of the registration statement as confirmation
of the fact that those requesting acceleration are aware of their respective responsibilities under
the Securities Act of 1933 and the Securities Exchange Act of 1934 as they relate to the proposed
public offering of the securities specified in the above registration statement.  Please allow
adequate time for us to revie w any amendment prior to the requested effective date of the
registration statement.

Kim D. Blickenstaff
Tandem Diabetes Care, Inc.
October 29, 2013
Page 3

 You may contact Jeanne Bennett  at (202) 551-3606  or Brian Cascio, Accounting Branch
Chief,  at (202) 551-3676  if you have questions regarding comments on the financial statements
and related matters.  Please contact Joseph McCann  at (202) 551-6262 or Mary Beth Breslin ,
Senior Attorney, at (202) 551-3625  with any other questions.

Sincerely,

 /s/ Mary Beth Breslin for

 Amanda Ravitz
Assistant Director

cc (via email):  Ryan C. Wilkins , Esq.  – Stradling Yocca Carlson & Rauth, P.C.