Loose nails are a cause for concern because they can catch and tear away from the nail bed. Most often caused by trauma, they can also result from fungal infection, poor circulation oe nutrition, or hypothyroidism. It is best to trim a loose nail as short as is comfortably possible. The shorter nail maybe less attractive , but it will also be less vulnerable to injury.
Protecting the loose nail with an adhesive bandage or piece of tape is also a good idea. After the loose nail has been trimmed away or falls off on its own, you may want to treat the nail bed with a topical antifugal daily until the new nail has advanced to the end of the toe.
This can take up to ten months.Treating the nail with an antifugal will help to avoid some of the nail changes that can occur after a nail has loosened or fallen off.
Reference: Great Feet For Life: Paul Langer : DPM