Any tips on keeping clumps out of the Optifast soup?

IMO opinion that stuff is highway robbery and nasty. My sympathies.

My doctor required me to get it or else I wouldn't have :/

I read an interesting tidbit on UnJury's website: For all powders?utm_source=BariatricPal&utm_medium=Affiliate&utm_campaign=CommentLink" target="_ad" data-id="1" >unjury flavors, do not use in liquids hotter than 140º F. Proteins, when heated, change texture. For example, you have seen an egg white go from a clear gel, to firm white, when cooked. For UNJURY, in a hot liquid, the proteins tend to clump. A food thermometer is a good way to get the temperature nicely warm...just right.

I'm going to assume that Optifast is a Protein powder of some sort; then my tidbit of information helps. If it's not, I have no more advice to give.

Use a whisk I used to love the chicken soup but you do have to blend well

Don't pour hot water into the soup, pour warm water and then re heat. So sorry about the optifast my DR required it too for my pre opt. The soup is best with added spices.