diff --git a/README.md b/README.md
index 788ceba..7d0b2a3 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,10 @@ so you can use external, third-party checks in your monitoring setup.
 with uptimerobot.com you might have more checks defined than this script
 will handle.*
 
+If you do not have a pro account, any scrape interval shorter than
+`scrape_interval: 5m` for this exporter will a) produce duplicated data
+and b) misuse uptimerobots API.
+
 ## Requirements
 
 * Python