My doctor says that his botox is 2 units per .1 cc. Does that sound correct?

Thank you for your question about botox.  Botox does not start working for at least 10-14 days post treatment.  However, the benefits should last 3-4 months.  The amount of units needed differs from person to person.  The reconstitution of botox varies from office to office.  You may hear terms of "1:1 or 2:1"  this is done in order to achieve different looks in different areas.  Either way, a unit of botox does not change. It is reconstituted differently in order to target specific muscle groups and achieve natural results. 
It is also important to keep in mind that several treatments may be required before more severe lines soften.  Regardless, it is important to decrease the muscle movement in order to improve moderate to severe wrinkles and fine lines.

To be sure, see two or more experienced, licensed and board-certified providers in your area for a complete evaluation to make sure you are a good candidate and that it is safe for you to have treatment. I hope this helps.

You can dilute Botox to nearly any concentration you desire. Generally the botox insert recommends that it be prepared at 4 units per cc

Moast doctors use more concentrated units than you have had but that dilution of 5 ccs of water to one vial of 100 units of Botox was used more in the earlier days of Botox. If it is diluyed more then there is a concern of affecting nearby muscles that should not get treated.