...I wouldn't wait any longer to begin the treatment for an amoebic infection (Flagyl). The treatment is not particularly dangerous, and starting early gives you the best chance of recovery. Waiting to see if it gains weight may allow time for secondary problems to occur and those are very hard to deal with at that point.
It should also be noted that Flagyl is very bitter. Placing it in food may result in it being ignored - twice as bad (no food or medicine). So individual oral dosing with a suspension is best. Your vet can do this for you, or you can email me and I’ll explain how to go about making it (assuming you get the first part, the Flagyl).
Again there are other causes of weight loss (as already pointed out). But an amoeba should be on of the first things suspected in Crestd Geckos. If you jump right on it - you will save your gecko.
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-Randy May
www.neoscales.com
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