What Is It?

[lynbrown]

I saw a small round silver looking object at the back of Theresa's upper arm. What is it?

[Sam1960]

see here lyn .......
https://www.thesun.co.uk/news/4807643/diabetic-theresa-may-reveals-patch-which-monitors-her-blood-sugar-as-she-walks-the-red-carpet-at-awards-ceremony/

[-SharonA-]

She has diabetes and wears an insulin patch.

[Old_Geezer]

It's where the silver bullet wounded her, last full moon.

[ethandron]

It’s not an insulin patch or a silver bullet wound. It’s a freestyle libre blood glucose monitoring device which helps type 1 diabetes sufferers closely monitor their blood glucose levels so they can adjust their insulin requirements to more closely mimic a non diabetic person.
Google it and educate yourselves.