Clinical Realities

What the Research Shows

In the SURMOUNT-1 DXA substudy, tirzepatide produced approximately 25% lean mass loss and 75% fat mass loss of total weight lost at 72 weeks. The STEP 1 DXA substudy showed semaglutide resulted in approximately 39% lean mass. A systematic review found lean mass constituted approximately 20–40% of total weight lost, pooled estimate near 30%. "Ozempic face" reflects subcutaneous facial fat loss proportional to total fat loss — not a unique drug effect.

What the Research Shows

The STEP 4 extension demonstrated that participants who discontinued semaglutide regained approximately two-thirds of prior weight loss over 48 weeks. A 2025 meta-analysis found pooled regain of 5.63 kg. Real-world data suggest approximately 60% regained by 1 year, though regain decelerates rather than continuing linearly.

What the Research Shows

In a small study of PCOS patients, approximately 80% who responded to semaglutide (≥5% weight loss) restored regular menstrual cycles within 6 months. Tirzepatide's prescribing information warns delayed gastric emptying may reduce oral contraceptive bioavailability. Non-oral methods (IUD, implant, patch, ring) are unaffected. Guidance recommends discontinuing GLP-1 RAs at least 2 months before planned conception.

What the Research Shows

The FDA's meta-analysis of 91 RCTs (107,910 participants) found no increased risk, leading to removal of the suicidal ideation warning in early 2025. A Nature Mental Health analysis of 374 studies concluded GLP-1 RAs had broadly beneficial effects on mental health outcomes.

What the Research Shows

GI adverse events affect 40–70% of patients, with nausea most frequent (42%). GLP-1 RA-mediated slowing involves direct smooth muscle signaling — not vagal nerve damage. Symptoms typically diminish as tolerance develops. Rare persistent cases after discontinuation have been reported.

What the Research Shows

An international cohort study found no increased thyroid cancer risk (pooled HR 0.81). Rodent C-cells express high GLP-1 receptor levels; human C-cells have minimal expression. Studies acknowledge median follow-up may be insufficient given MTC's 10+ year latency.

What the Research Shows

A meta-analysis of 11 RCTs found GLP-1 RAs reduced composite kidney outcomes by 18% and kidney failure by 16%. Real-world data showed users with prior stone history had lower recurrence (28% vs. 43.5%). Adequate hydration during dose escalation remains important.

What the Research Shows

Rapid loss exceeding 25% body weight in under 12 months exceeds the skin's remodeling capacity. Total magnitude is the strongest predictor. No data show GLP-1 RA loss produces different outcomes than diet-induced loss of equivalent magnitude.

What the Research Shows

GLP-1 RAs block alcohol-induced dopamine release. A systematic review found significant AUDIT score reduction (−7.81 points). Delayed gastric emptying may increase blood alcohol concentration per unit consumed.

What the Research Shows

A review of 28 studies found overall drug exposure generally preserved. Significant changes: rosuvastatin (+64%), valsartan (+90%), and modeling predicts dabigatran may increase >200%. Oral contraceptive bioavailability significantly reduced with tirzepatide; levothyroxine absorption decreased with oral semaglutide.

What the Research Shows

Vitamin D: 7.5% at 6 months → 13.6% at 12 months. Over 60% below requirements for calcium and iron. Iron: 26–30% lower ferritin. B vitamins: 22.4% deficiency by 12 months. No standardized monitoring framework exists despite patterns mirroring bariatric surgery.

What the Research Shows

Prescription fills increased 442% between 2021–2023. During the shortage (2022–2025), FDA regulations permitted compounding pharmacies to produce copies. Both shortages now resolved; enforcement discretion ended spring 2025. Oral GLP-1 options, manufacturer savings programs, and Medicare pricing commitments signal movement toward affordability.