Here is a link to the Medical Advisory Criteria for Evaluation Under 49CFRPart391.41 

http://www.fmcsa.dot.gov/rules-regulations/administration/medical.htm

391.41(b)(3)

A person is physically qualified to drive a commercial motor vehicle if that person:

Has no established medical history or clinical diagnosis of diabetes mellitus currently requiring insulin for control.
DOT regulations for Diabetes

For those drivers who require Insulin as a Type 2 diabetic or Type MODY, to properly manage their blood glucose levels, or a Type 1, the person can obtain a waiver from FMCSA to either drive intrastate (within the state they live in) or interstate (traveling more than one state). 

In order to obtain the waiver you will have to be off of the truck and follow the guidelines set forth within the rules and regulations of FMCSA and it can take many months for the government to approve this waiver.  In addition to that there are many companies that do not accept the waivers.  


Here are some links to provide you with more information:

hhttp://www.fmcsa.dot.gov/facts-research/research-technology/tech/TB-02-01-1.htm


http://www.fmcsa.dot.gov/facts-research/research-technology/tech/TB-02-01-1.pdf

http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrguidedetails.aspx?menukey=381


Subpart C - Procedures for applying for exemptions

§ 381.310 How do I apply for an exemption?

(a) You must send a written request (for example, a typed or handwritten (printed) letter), which includes all of the information required by this section, to the Administrator, Federal Motor Carrier Safety Administration, 1200 New Jersey Ave., SE., Washington, DC 20590-0001.

(b) You must identify the person or class of persons who would be covered by the exemption. The application for an exemption must include:
     (1) Your name, job title, mailing address, and daytime telephone number;
     (2) The name of the individual or motor carrier that would be responsible for the use or operation of CMVs;
     (3) Principal place of business for the motor carrier (street address, city, State, and zip code); and
     (4) The USDOT identification number for the motor carrier.

(c) You must provide a written statement that:
     (1) Describes the reason the exemption is needed, including the time period during which it is needed;
     (2) Identifies the regulation from which you would like to be exempted;
     (3) Provides an estimate of the total number of drivers and CMVs that would be operated under the terms and conditions of the exemption;
     (4) Assesses the safety impacts the exemption may have;
     (5) Explains how you would ensure that you could achieve a level a safety that is equivalent to, or greater than, the level of safety that would be obtained by complying with the regulation; and
     (6) Describes the impacts (e.g., inability to test innovative safety management control systems, etc.) you could experience if the exemption is not granted by the FMCSA.

(d) Your application must include a copy of all research reports, technical papers, and other publications and documents you reference.
[63 FR 67608, Dec. 8, 1998, as amended at 72 FR 55700, Oct. 1, 2007]