The following nutrients are labeled in the supplement facts if they are present in measurable amounts:
-Calories from fat
A measurable amount is an amount that exceeds the amount that can be declared as "zero" in the nutrition label of conventional foods, as specified in 21 CFR 101.9(c). The definition for measurable amount varies from nutrient to nutrient.
Total calories may be expressed as zero if there are less than 5 calories per serving.
Sodium may be expressed as zero if there is less than 5 milligrams per serving.
Cholesterol may be expressed as zero if there is less than 2 milligrams per serving.
The following may be expressed as zero if there is less than 0.5 grams per serving.
Totals and percentages of vitamins and minerals present at less than 2 percent of the RDI (Reference Daily Intake) are not required to be expressed in nutrition labeling, but may be declared by a zero.
If you are looking for a particular nutrient on the label of your product and you do not see it, this is because it contains less than what is considered a "measurable amount", if it contains it at all.
If you would like more information on reading supplement labels, please visit this blog post.