I've done some readings, and perhaps it's more safe to withdraw blood prior hemo dialysis, since there are dialysis solutions (Potassium, Sodium, and of course Sugar substances), that may have some effects on the Triglycerides, not sure about LDL and HDL.
The center I use does lipid profile on an annual basis, and has me draw the tube for that pre-dialysis (with a 12 hour fast).