Hi, I'm 36 and in great health but I' have some annoying twitching in my right and left arm bicep and above left knee. What could cause this?

Low magnesium. can produce muscle twitches. Please see your doc first to rule out other causes. He/she may test your magnesium level if indicated. You can supplement w/magnesium. One good brand is called "Jigsaw magnesium." Peace and good health.
Twitching. On either zoloft or Synthroid (thyroxine) is not uncommon. You may with to check your thyroid profile on the current dose. If the twitching worsens check your kidney function (BUN /CR) electrolytes and if these are normal talk to a neurologist. www.healthtap.com/drericweisman (Neurology)