Exhibit 3.1

FOURTH AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

NEUROMETRIX, INC.

ARTICLE I

NAME

The name of the corporation is NeuroMetrix, Inc. (hereinafter called the “Corporation”).

ARTICLE II

REGISTERED AGENT

The address of the Corporation’s registered office in the State of Delaware is Corporation Service Company, 251 Little Falls Drive, City of Wilmington, County of New Castle, Delaware 19808. The name of the Corporation’s registered agent at such address is Corporation Service Company.

ARTICLE III

PURPOSE

The purpose of the Corporation is to engage in any lawful act or activity for which corporations may be organized under the DGCL.

ARTICLE IV

CAPITAL STOCK

4.1 Authorized Capital Stock. The total number of shares of capital stock which the Corporation shall have authority to issue is one thousand two hundred (1,200) shares, of which (i) one thousand (1,000) shares shall be a class designated as common stock, par value $0.0001 per share (the “Common Stock”), and (ii) two hundred (200) shares of preferred stock, par value $0.001 per share (the “Preferred Stock”).

4.2 Preferred Stock. The Board of Directors of the Corporation (the “Board”) is hereby expressly authorized to provide for the issuance of the Preferred Stock for one or more series of Preferred Stock and to establish or change from time to time the number of shares to be included in each such series and to fix the voting rights, if any, designations, powers, preferences and relative, participating, optional, special and other rights, if any, of each such series and any qualifications, limitations and restrictions thereof, as shall be stated in the resolution or resolutions adopted (including prior to, on or after the date hereof) by the Board providing for the issuance of such series and included in a certificate of designation (a “Preferred Stock Designation”) filed pursuant to the DGCL, and the Board is hereby expressly vested with the authority to the full extent provided by law, now or hereafter, to adopt any such resolution or resolutions.

4.3 Common Stock.

a. Voting.

(i) Except as otherwise required by law or this Fourth Amended and Restated Certificate (including any Preferred Stock Designation), the holders of the shares of Common Stock shall exclusively possess all voting power with respect to the Corporation.

(ii) Except as otherwise required by law or this Fourth Amended and Restated Certificate (including any Preferred Stock Designation), the holders of shares of Common Stock shall be entitled to one vote for each such share on each matter properly submitted to the stockholders of the Corporation on which the holders of the shares of Common Stock are entitled to vote.

(iii) Except as otherwise required by law or this Fourth Amended and Restated Certificate (including any Preferred Stock Designation), at any annual or special meeting of the stockholders of the Corporation, the holders of the shares of Common Stock shall have the exclusive right to vote for the election of directors and on all other matters properly submitted to a vote of the stockholders of the Corporation. Notwithstanding the foregoing, except as otherwise required by law or this Fourth Amended and Restated Certificate (including any Preferred Stock Designation), the holders of the shares of Common Stock shall not be entitled to vote on any amendment to this Fourth Amended and Restated Certificate (including any amendment to any Preferred Stock Designation) that relates solely to the terms of one or more outstanding series of Preferred Stock if the holders of such affected series of Preferred Stock are entitled, either separately or together with the holders of one or more other such series, to vote thereon pursuant to this Fourth Amended and Restated Certificate (including any Preferred Stock Designation) or the DGCL.

b. Dividends. Subject to applicable law, the rights, if any, of the holders of any outstanding series of the Preferred Stock, the holders of the shares of Common Stock shall be entitled to receive such dividends and other distributions (payable in cash, property or capital stock of the Corporation) when, as and if declared thereon by the Board from time to time out of any assets or funds of the Corporation legally available therefor and shall share equally on a per share basis in such dividends and distributions.

c. Liquidation, Dissolution or Winding Up of the Corporation. Subject to applicable law, the rights, if any, of the holders of any outstanding series of the Preferred Stock, in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Corporation, after payment or provision for payment of the debts and other liabilities of the Corporation, the holders of the shares of Common Stock shall be entitled to receive all the remaining assets of the Corporation available for distribution to its stockholders, ratably in proportion to the number of shares of Common Stock held by them.

ARTICLE V

STOCKHOLDER ACTION

5.2 Action without Meeting. Except as otherwise provided herein, any action required or permitted to be taken by the stockholders of the Corporation at any annual or special meeting of stockholders of the Corporation must be effected at a duly called annual or special meeting of stockholders and may not be taken or effected by a written consent of stockholders in lieu thereof.

5.3 Special Meetings. Except as otherwise required by statute and subject to the rights, if any, of the holders of any series of Preferred Stock, special meetings of the stockholders of the Corporation may be called only by the Board of Directors acting pursuant to a resolution approved by the affirmative vote of a majority of the Directors then in office. Only those matters set forth in the notice of the special meeting may be considered or acted upon at a special meeting of stockholders of the Corporation.

ARTICLE VI

DIRECTORS

6.1 General. The business and affairs of the Corporation shall be managed by or under the direction of the Board of Directors except as otherwise provided herein or required by law.

6.2 Election of Directors. Election of Directors need not be by written ballot unless the Bylaws of the Corporation (the “Bylaws”) shall so provide.

6.3 Number of Directors; Term of Office. The number of Directors of the Corporation shall be fixed solely and exclusively by resolution duly adopted from time to time by the Board of Directors. The Directors, other than those who may be elected by the holders of any series of Preferred Stock, shall be classified, with respect to the term for which they severally hold office, into three classes, as nearly equal in number as reasonably possible. The Directors of the Corporation initially will be assigned to be Class I Directors, Class II Directors and Class III Directors of the Corporation in accordance with a resolution or resolutions adopted by the Board of Directors. The initial Class I Directors served for a term expiring at the annual meeting of stockholders held in 2005, the initial Class II Directors served for a term expiring at the annual meeting of stockholders held in 2006, and the initial Class III Directors served for a term expiring at the annual meeting of stockholders held in 2007. At each annual meeting of stockholders, Directors elected to succeed those Directors whose terms expire shall be elected for a term of office to expire at the third succeeding annual meeting of stockholders after their election. Notwithstanding the foregoing, the Directors elected to each class shall hold office until their successors are duly elected and qualified or until their earlier resignation or removal.

Notwithstanding the foregoing, whenever, pursuant to the provisions of Article IV of this Certificate, the holders of any one or more series of Preferred Stock shall have the right, voting separately as a series or together with holders of other such series, to elect Directors at an annual or special meeting of stockholders, the election, term of office, filling of vacancies and other features of such directorships shall be governed by the terms of this Certificate and any certificate of designations applicable thereto.

6.4 Vacancies. Subject to the rights, if any, of the holders of any series of Preferred Stock to elect Directors and to fill vacancies in the Board of Directors relating thereto, any and all vacancies in the Board of Directors, however occurring, including, without limitation, by reason of an increase in size of the Board of Directors, or the death, resignation, disqualification or removal of a Director, shall be filled solely and exclusively by the affirmative vote of a majority of the remaining Directors then in office, even if less than a quorum of the Board of Directors, and not by the stockholders. Any Director appointed in accordance with the preceding sentence shall hold office for the remainder of the full term of the class of Directors in which the new directorship was created or the vacancy occurred and until such Director’s successor shall have been duly elected and qualified or until his or her earlier resignation or removal. Subject to the rights, if any, of the holders of any series of Preferred Stock to elect Directors, when the number of Directors is increased or decreased, the Board of Directors shall, subject to Article VI.3 hereof, determine the class or classes to which the increased or decreased number of Directors shall be apportioned; provided, however, that no decrease in the number of Directors shall shorten the term of any incumbent Director. In the event of a vacancy in the Board of Directors, the remaining Directors, except as otherwise provided by law, shall exercise the powers of the full Board of Directors until the vacancy is filled.

6.5 Removal. Subject to the rights, if any, of any series of Preferred Stock to elect Directors and to remove any Director whom the holders of any such stock have the right to elect, any Director (including persons elected by Directors to fill vacancies in the Board of Directors) may be removed from office (i) only with cause and (ii) only by the affirmative vote of the holders of 75% or more of the shares then entitled to vote at an election of Directors. At least forty-five (45) days prior to any meeting of stockholders at which it is proposed that any Director be removed from office, written notice of such proposed removal and the alleged grounds thereof shall be sent to the Director whose removal will be considered at the meeting.

ARTICLE VII

LIMITATION OF LIABILITY

A Director of the Corporation shall not be personally liable to the Corporation or its stockholders for monetary damages for breach of fiduciary duty as a Director, except for liability (a) for any breach of the Director’s duty of loyalty to the Corporation or its stockholders, (b) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (c) under Section 174 of the DGCL or (d) for any transaction from which the Director derived an improper personal benefit. If the DGCL is amended after the effective date of this Certificate to authorize corporate action further eliminating or limiting the personal liability of Directors, then the liability of a Director of the Corporation shall be eliminated or limited to the fullest extent permitted by the DGCL, as so amended.

Any repeal or modification of this Article VII by either of (i) the stockholders of the Corporation or (ii) an amendment to the DGCL, shall not adversely affect any right or protection existing at the time of such repeal or modification with respect to any acts or omissions occurring before such repeal or modification of a person serving as a Director at the time of such repeal or modification.

ARTICLE VIII

AMENDMENT OF BYLAWS

8.1 Amendment by Directors. Except as otherwise provided by law, the Bylaws may be amended or repealed by the Board of Directors by the affirmative vote of a majority of the Directors then in office.

8.2 Amendment by Stockholders. The Bylaws may be amended or repealed at any annual meeting of stockholders, or special meeting of stockholders called for such purpose as provided in the Bylaws, by the affirmative vote of at least 75% of the outstanding shares entitled to vote on such amendment or repeal, voting together as a single class; provided, however, that if the Board of Directors recommends that stockholders approve such amendment or repeal at such meeting of stockholders, such amendment or repeal shall only require the affirmative vote of the majority of the outstanding shares entitled to vote on such amendment or repeal, voting together as a single class.

ARTICLE IX

AMENDMENT OF CERTIFICATE OF INCORPORATION

The Corporation reserves the right to amend or repeal this Certificate in the manner now or hereafter prescribed by statute and this Certificate, and all rights conferred upon stockholders herein are granted subject to this reservation. Whenever any vote of the holders of voting stock is required to amend or repeal any provision of this Certificate, and in addition to any other vote of holders of voting stock that is required by this Certificate or by law, such amendment or repeal shall require the affirmative vote of the majority of the outstanding shares entitled to vote on such amendment or repeal, and the affirmative vote of the majority of the outstanding shares of each class entitled to vote thereon as a class, at a duly constituted meeting of stockholders called expressly for such purpose; provided, however, that the affirmative vote of not less than 75% of the outstanding shares entitled to vote on such amendment or repeal, and the affirmative vote of not less than 75% of the outstanding shares of each class entitled to vote thereon as a class, shall be required to amend or repeal any provision of Article V, Article VI, Article VII, Article VIII or Article IX of this Certificate.

ARTICLE X

EXCLUSIVE FORUM FOR CERTAIN LAWSUITS

10.1 Forum. Unless the Corporation consents in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware shall be the sole and exclusive forum for any stockholder (including a beneficial owner) to bring (i) any derivative action or proceeding brought on behalf of the Corporation, (ii) any action asserting a claim of breach of a fiduciary duty owed by any director, officer or other employee of the Corporation to the Corporation or the Corporation’s stockholders, (iii) any action asserting a claim against the Corporation, its directors, officers or employees arising pursuant to any provision of the DGCL or this Fourth Amended and Restated Certificate or the Bylaws, or (iv) any action asserting a claim against the Corporation, its directors, officers or employees governed by the internal affairs doctrine and, if brought outside of Delaware, the stockholder bringing the suit will be deemed to have consented to service of process on such stockholder’s counsel except any action (A) as to which the Court of Chancery in the State of Delaware determines that there is an indispensable party not subject to the jurisdiction of the Court of Chancery (and the indispensable party does not consent to the personal jurisdiction of the Court of Chancery within ten days following such determination), (B) which is vested in the exclusive jurisdiction of a court or forum other than the Court of Chancery, (C) for which the Court of Chancery does not have subject matter jurisdiction, or (D) any action arising under the Securities Act of 1933, as amended. Notwithstanding the foregoing, the provisions of this Section 10.1 will not apply to suits brought to enforce any liability or duty created by the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction.

10.2 Consent to Jurisdiction. If any action the subject matter of which is within the scope of Section 10.1 immediately above is filed in a court other than a court located within the State of Delaware (a “Foreign Action”) in the name of any stockholder, such stockholder shall be deemed to have consented to (i) the personal jurisdiction of the state and federal courts located within the State of Delaware in connection with any action brought in any such court to enforce Section 10.1 immediately above (an “FSC Enforcement Action”) and (ii) having service of process made upon such stockholder in any such FSC Enforcement Action by service upon such stockholder’s counsel in the Foreign Action as agent for such stockholder.

ARTICLE XI

SEVERABILITY

If any provision or provisions (or any part thereof) of this Fourth Amended and Restated Certificate shall be held to be invalid, illegal or unenforceable as applied to any person, entity or circumstance for any reason whatsoever, then, to the fullest extent permitted by law, (i) the validity, legality and enforceability of such provisions in any other circumstance and of the remaining provisions of this Fourth Amended and Restated Certificate (including, without limitation, each portion of any paragraph of this Fourth Amended and Restated Certificate containing any such provision held to be invalid, illegal or unenforceable that is not itself held to be invalid, illegal or unenforceable) and the application of such provision to other persons or entities and circumstances shall not in any way be affected or impaired thereby, and (ii) the provisions of this Fourth Amended and Restated Certificate (including, without limitation, each portion of any paragraph of this Fourth Amended and Restated Certificate containing any such provision held to be invalid, illegal or unenforceable) shall be construed so as to permit the Corporation to protect its directors, officers, employees and agents from personal liability in respect of their good faith service or for the benefit of the Corporation to the fullest extent permitted by law.

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