[header] How to diagnose heart failure in gerbils [title] Monitor your gerbil's weight. [step] Sudden weight gain can indicate heart failure in gerbils. Purchase a digital scale, and weigh your gerbil at least once a week. 
If you notice any significant weight gain, call a veterinarian as soon as possible. [substeps] To weigh your gerbil, place it on the scale and use your hands to brace the gerbil lightly without putting any pressure on the scale.