What does Bilirubin level of 1.6 and SGPT level of 25 signify?

The SGPT (also known as ALT) is a liver enzyme. In most labs 25 is normal.

Bilirubin is a break down product of hemoglobin that is cleared by the liver (and kidneys). The mildly elevated level of 1.6 can be harmless normal variant (Glibert's Syndrome), lab error or due to some other illness such as a liver problems, gall stone, or increase red cell production.

If the other labs are normal and you are feeling well (or had recently had a cold) it is probably the the first option.