Registered dietitian here. The GI changes on GLP-1 meds causing new dairy sensitivities is something I see ALL the time in my practice. The delayed gastric emptying means whey concentrate (which has more lactose) sits in your stomach longer and ferments. It's not a true allergy — it's a mechanical issue.

My recommendations by category:

Whey Isolate (lower lactose):

• Dymatize ISO100 — 25g protein, <1g lactose, mixes beautifully. Gourmet Chocolate is the gold standard flavor imo
• Isopure Zero Carb — 25g protein, lactose-free, unflavored version is great for cooking

Casein:

• I'd actually AVOID casein on GLP-1 meds. It forms a gel in the stomach and digests even slower than whey. With already-delayed gastric emptying, this can make nausea significantly worse

Plant-based:

• Momentous Essential Plant — 20g protein, pea/rice blend, tastes surprisingly good
• Garden of Life Sport Organic — 30g protein, but chalky texture unless blended
• Ghost Vegan — 20g protein but honestly the flavor is the best in the plant category. Peanut Butter Cereal Milk is unreal

My top recommendation for GLP-1 patients: start with a whey ISOLATE before jumping to plant. Most people tolerate isolate just fine because the lactose has been filtered out.

I'll die on the plant protein hill. Been using Orgain Organic Protein for 8 months on tirzepatide and it's been flawless. 21g protein per scoop, no bloating, no gas, no nausea spikes.

The trick with plant proteins is you HAVE to use a blender or at minimum a BlenderBottle with one of those wire balls. If you just stir it with a spoon you're drinking wet sand.

My daily shake recipe that I can get down even on bad nausea days:

• 1 scoop Orgain Creamy Chocolate Fudge
• 1 cup unsweetened almond milk (30 cal)
• 1/2 frozen banana
• 1 tbsp PB2 powdered peanut butter
• 3 ice cubes

Macros: 270 cal / 28g protein / 32g carbs / 6g fat

Tastes like a Wendy's frosty. I'm not even kidding.

oh wow I didn't even think about the isolate vs concentrate distinction. I just looked at my ON Gold Standard tub and yep — it's a concentrate/isolate BLEND, so there IS lactose in there. That explains a lot.

Good call on avoiding casein. I was actually about to order some because I read it keeps you fuller longer and I was like "perfect for overnight" but that makes total sense that it would be miserable with delayed emptying.

that recipe sounds amazing actually. Does Orgain have any gritty texture? That's my #1 fear with plant proteins.

Slight grittiness if you just shake it, but blended it's completely smooth. The banana helps a lot with texture too. It's pea protein based so it'll never be AS silky as whey isolate, but honestly after a week you stop noticing.

Biggest downside is the protein per scoop is lower. At 21g vs whey isolate's 25-30g, you either need more scoops or need to supplement with other protein sources. On GLP-1 when every calorie counts, that efficiency matters.