I am 36 years old and have noticeable sagging skin / turkey neck. What is the best treatment for this?

You do not appear to have loose sagging skin.  It appears you may have a tight platysma band which can be ascertained on physical examination. Botox or surgical release of the bands may be appropriate.  Thermage or Ultherapy will likely be disappointing.

Hello and thank you for your excellent question. If you're unhappy with the laxity of the skin on your neck, then you would be a good candidate for Ultherapy, this will help tighten the skin. However, you also have a platysmal band (this is the vertical line you see running up and down the neck. Platysmal bands can be addressed with Botox, surgical release, or a necklift. You should consult with a board certified plastic surgeon in your area for more information. 

Thank you for your question. In your case, I would likely recommend a non-surgical skin tightening technique like Ultherapy or Thermage. These devices deliver controlled heating into the deeper dermal structure to constrict tissue and firm skin from the inside out. In addition, the treatments stimulate the body to produce more collagen for results that are both natural and long-lasting. Make sure you are working with an experienced, board-certified dermatologist who can tailor your treatment to your precise needs and goals.