If your turtle is constipated, you obviously can't get a fecal sample.
Your veterinarian may be able to obtain a sample by using a probe.
If your turtle is eliminating, the best way to obtain the sample is to
feed the turtle in a separate container and wait until it procudes the
sample. This commonly happens within half an hour of feeding.
Take the sample as soon as it is produced and put it, including some
water, into a small container. (For example, you can scoop it out with
a cleaned yogurt cup.) Seal the container and refrigerate (never freeze
a sample) the sample until used.
It is best if a sample is less than 4 hours old when it gets to the