To check this you should use Query Inspector (new in Grafana v4.5). The query Inspector shows query requests and responses.
For more on the query insector read [this guide here](https://community.grafana.com/t/using-grafanas-query-inspector-to-troubleshoot-issues/2630). For
For more on the query inspector read [this guide here](https://community.grafana.com/t/using-grafanas-query-inspector-to-troubleshoot-issues/2630). For
older versions of Grafana read the [how troubleshoot metric query issue](https://community.grafana.com/t/how-to-troubleshoot-metric-query-issues/50/2) article.