Inter-lab variability in peptide testing — why results differ between labs — COA & Analytical Testing

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Feb 2024

Research Triangle, NC

May 21, 2026 at 8:08 AM#1

Had my annual physical last week and my PCP literally said "these results are too good — what are you doing differently?" I've been on semaglutide 1.0mg for 7 months and lost 52 lbs. Didn't tell him about compound sema. Here are the before/after: | Marker | Jan 2025 | Aug 2025 | Ref Range | |--------|----------|----------|-----------| | A1C | 6.8% | 5.2% | <5.7% | | Fasting glucose | 132 mg/dL | 89 mg/dL | 70-100 | | Triglycerides | 312 mg/dL | 118 mg/dL | <150 | | LDL | 168 mg/dL | 102 mg/dL | <100 | | HDL | 34 mg/dL | 51 mg/dL | >40 | | ALT | 58 U/L | 22 U/L | 7-56 | | CRP | 8.4 mg/L | 1.1 mg/L | <3.0 | He kept asking if I was on a new medication. I just said "diet and exercise." Now I feel guilty for not being transparent but I also don't want a lecture about compounding pharmacies. Anyone else deal with this?

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sean_dublin

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Dublin, IE

May 21, 2026 at 8:16 AM#2

I'll be the unpopular opinion here — you should tell your doctor. Not because of any moral obligation, but because your doctor NEEDS to know what medications you're on for your own safety. If you ever need surgery, have a drug interaction, or develop pancreatitis, they need the full picture. That said, your labs are genuinely incredible. The CRP drop from 8.4 to 1.1 alone is massive — that's systemic inflammation plummeting. The triglyceride improvement is also wild. GLP-1s do have direct cardiovascular benefits beyond weight loss, so these numbers track.

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pete_nash

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Nashville, TN

May 21, 2026 at 8:24 AM#3

I'm in the exact same boat. My endo noticed my A1C dropped from 7.1 to 5.4 in 5 months and was like "this doesn't happen with lifestyle changes alone at your age." I eventually told her. She wasn't thrilled about the compounding pharmacy but she said she'd rather know and monitor me properly. She actually started ordering more specific labs after that — lipase, amylase, thyroid panel. Worth considering.

Last edited: May 21, 2026 at 2:24 PM

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Dr.PeteFamMed

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Minneapolis, MN

May 21, 2026 at 8:32 AM#4

Those numbers are legitimately impressive but also totally consistent with what we see in the STEP trials. The SELECT trial showed semaglutide reducing MACE events by 20%. Your CRP dropping like that is basically the anti-inflammatory effect in action. Your HDL going from 34 to 51 is the one that would really raise eyebrows though. That's hard to achieve with medication alone — usually takes significant sustained exercise on top of it. Did you increase cardio?

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Dr.GutHealth

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Minnesota

May 21, 2026 at 9:14 AM#5

Yeah I've been walking 8-10k steps daily which is a huge change from my previous couch lifestyle. And I started lifting 3x/week about 3 months in. So the HDL bump is probably combination of the sema + actual movement. You're right and I know it. I think I'm going to tell him at my follow-up in October. I just need to find the right way to frame it.

Inter-lab variability in peptide testing — why results differ between labs

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