There are several tool that can be adapted / used for that. Some of them that are the most common:

1. Duke Social Support Index (DSSI) – 10 item scale; see: http://www.apcrc.nhs.uk/library/knowledge_bulletins/documents/SocialIsolation&Loneline ss.pdf

2. Lubben Social Network Scale (LSNS) – including a 6-item scale; see: https://www.bc.edu/schools/gssw/lubben/description_of_thelsns.html

3. Social Disconnectedness – 8-item scale (Cornwell and Waite, 2009) [these authors also described a Perceived Isolation Scale]; see, e.g.: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756979/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2800811/

I hope those helped.

Best regards