Every lot of emulsion should ship with a certificate of analysis from an independent laboratory. Most of the page is a pass or fail list. A few lines are the ones a formulator actually uses.
Potency. The concentration of each cannabinoid in milligrams per millilitre or milligrams per gram. This is the number you dose from, and it should be reported per lot, not as a nominal value.
Density. Needed to convert between volume and weight. If you dose by weight, which is more repeatable, you cannot skip this.
Droplet size and distribution. The mean droplet size tells you how fine the emulsion is. The distribution, often reported as a polydispersity index, tells you how uniform it is. A low mean with a wide distribution is a warning sign: the large tail is what creams and scalps.
Microbials, heavy metals, residual solvents and pesticides. These are the safety panels. They should all be present and all pass, and the lab should be accredited.
Date and lot number. A COA without both is decoration. The lot number should match the container, and the date should be recent enough that the material is inside its shelf life.
If a supplier cannot produce a COA with all of these, or produces one that reads the same on every lot, ask why.