Hi,
Thanks for your query.
It seems that you have muscle twitches or fasciculations. These are small, local, involuntary muscle contraction and relaxation visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers.
You might consult your doctor who can order
1. a few blood tests including thyroid function tests,
2. Serum electrolytes including Serum calcium and potassium levels.
3. Serum B12 levels

In case the above tests are normal further testing can be done including - nerveconduction studies, Electromyography, etc. These tests might help to diagnose any underlying neurological issues.

I do hope that you have found something helpful and I will be glad to answer any further query.
Take care

Hi Dear,

Welcome to HCM.

Understanding your concern. As per your query you twitch in left arm for the past week off and on. Well there can be many reasons for symptoms you mention in query like stress and anxiety , caffeine and other stimulants , nutritional deficiencies , smoking , reaction to drugs, such as corticosteroids, stimulants, and estrogen , muscular dystrophy , nerve compression or Isaac’s syndrome . I would suggest you to eat fresh vegetables and fruits , drink plenty of water , apply warm compresses to your arms and do light stretching and relaxing exercises like yoga . If condition doesn't get well then consult orthopedic surgeon for proper examination . Doctor may order certain test like blood test , physical examination , nerve conduction test and take history to confirm the diagnosis and treatment . Doctor may prescribe nerve supplement , anti inflammatory along with muscle relaxant and physical therapy.

Hope your concern has been resolved.

Get Well Soon.

Best Wishes,
Dr. Harry Maheshwari