One the things that has helped me is Vitamin D.
Sometimes anxiety can result from shallow breathing and hyperventilation--when you aren't even aware that you are doing it--so be conscious of your breathing.
When anxiety comes on, sit quietly and breathe. Try this--I call it triangle breathing because I picture a triangle as I do it.
Sit and take a nice slow, deep breath to the count of four (up the first side of the triangle.)
Then breathe out, slowly to 4 counts (down the other side of the triangle)
Then as the last breath goes out hold your breath for four counts (across the bottom of the triangle)
and repeat several times. A doctor told me this increases the carbon dioxide in the blood and relieves anxiety and I have found this works very well. I use it all the time.
1) it gets your mind off of the anxiety and 2) it really calms your heightened feelings. Don't get discouraged if it doesn't work right away--keep at it, staying calm and knowing you are safe and what you are feeling is awful but just a feeling and it WILL go away.
best of luck!