I weighed myself at the hospital.

[Kumarc]

I weighed myself at the hospital. The machine showed my weight-70 kg.

Is the sentence correct in a conversation?

 

[emsr2d2]

I weighed myself at the hospital. The machine scales showed my weight to be 70 kg.

See above.

Is the sentence correct in a conversation?

We tend to think of everything as potentially being part of a conversation. If this was something you were simply going to say to yourself at home with no one else around, you wouldn't need to worry whether it was correct. (Also, it would be a strange thing to say to yourself!)