Prescription medications that copy a gut hormone released after eating, given by injection or as a tablet, to quiet appetite. Trials show sustained weight loss, better blood sugar, fewer heart attacks and strokes, lower death rates — but only in people carrying excess weight, diabetes or heart disease. Digestive side effects are common, a meaningful share of the weight lost is muscle, and most benefit disappears within a year of stopping. (Full Review)

Protocol

Standard conventional protocol

Semaglutide 0.25 → 2.4 mg weekly

Labelled titration subcutaneously, one step every 4 weeks (0.25, 0.5, 1.0, 1.7, 2.4 mg). Tirzepatide 2.5 mg weekly, then 2.5 mg increases every 4 weeks to a maximum of 15 mg. Oral semaglutide 3 mg daily for 30 days, then 7 mg, then 14 mg.

Longevity-oriented low-dose or "microdosing" protocol

Semaglutide 0.125–0.5 mg weekly

Held indefinitely in longevity and functional-medicine clinics. Neither approach is the default: the conventional protocol has all the outcome evidence behind it, the low-dose protocol none.

Best time of day

Same weekly day, any hour

Timing within the day is pharmacologically irrelevant for weekly agents; the dose may be moved by up to 2 days. Oral semaglutide is the exception: on waking, fasted, no more than 120 mL of water, at least 30 minutes before food, drink, or other medication.

Time to effect

Weight loss

2–4 weeks

Appetite suppression is usually noticeable within the first week. Loss continues for roughly 60–72 weeks before plateauing, so a judgment made at 3 months underestimates the eventual effect.

Glycemic improvement

12 weeks

Substantially complete by 12 weeks. Steady state at each dose step is reached only after 4–5 weeks given the ~7-day half-life of semaglutide.

Cardiovascular and kidney benefit

1–3 years

The interval over which these benefits emerged in the trials. Full washout after stopping takes 5–6 weeks.

Benefits

High: Substantial and sustained weight reduction; improved glycemic control and prevention of type 2 diabetes; reduced major adverse cardiovascular events; reduced all-cause mortality in higher-risk populations; slowed kidney function decline

Medium: Reduced systemic inflammation; lower blood pressure and improved lipid profile; improved obstructive sleep apnea; reduced symptoms and events in heart failure with preserved ejection fraction; resolution of fatty liver disease and steatohepatitis; reduced knee osteoarthritis pain; improved walking capacity in peripheral artery disease; reduced craving and consumption of alcohol and other rewarding substances

Low: Reduced incidence of obesity-associated cancers; slowed epigenetic aging; reduced dementia incidence, conflicted; improved ovulatory function in polycystic ovary syndrome

Speculative: Weight-independent geroprotection; benefit in metabolically healthy, normal-weight adults using low doses

Contraindications

Personal or family history of medullary thyroid carcinoma, or known MEN2

Prior serious hypersensitivity to the agent

Pregnancy or attempted conception (stop at least two months before conception for semaglutide); breastfeeding

Type 1 diabetes as monotherapy

Strong caution: prior acute pancreatitis of any cause; established gastroparesis or gastric outlet obstruction

Strong caution: active or historical anorexia nervosa or bulimia nervosa; BMI below 20 kg/m² without a metabolic indication

Strong caution: active proliferative diabetic retinopathy with HbA1c above roughly 9%; severe hepatic impairment (Child-Pugh Class C); eGFR below 15 mL/min/1.73 m² or dialysis dependence

Strong caution: any elective procedure requiring general anesthesia within the following week

Key Interactions

Insulin and sulfonylureas (glimepiride, glipizide, glyburide): hypoglycemia

Oral medications with narrow therapeutic windows (warfarin, levothyroxine, digoxin, lithium, phenytoin): unpredictable levels

Oral contraceptives (combined ethinylestradiol with levonorgestrel or norgestimate): reduced contraceptive efficacy

Diuretics (furosemide, hydrochlorothiazide, spironolactone), ACE inhibitors (lisinopril, ramipril, enalapril), ARBs (losartan, valsartan, telmisartan), NSAIDs (ibuprofen, naproxen): compounded volume depletion, acute kidney injury

Antacids (calcium carbonate, magnesium hydroxide), proton pump inhibitors (omeprazole, esomeprazole, pantoprazole), bulk-forming laxatives (psyllium, methylcellulose), loperamide, alcohol: impaired oral semaglutide absorption, constipation or ileus

Supplements with additive glucose-lowering effects (berberine, Gymnema sylvestre, bitter melon, alpha-lipoic acid, chromium picolinate, cinnamon extract): additive hypoglycemia

Supplements affected by, or affecting, this class (iron, calcium, vitamin B12, vitamin D, high-dose turmeric or curcumin, psyllium): altered status or absorption

Metformin (additive gastrointestinal burden); SGLT2 inhibitors (empagliflozin, dapagliflozin): additive cardiorenal protection

Protein powders, creatine monohydrate, vitamin D, electrolytes: no restriction, deliberately additive

Risk & Side Effects

High: Gastrointestinal adverse events; loss of lean mass, conflicted; weight regain after discontinuation; gallbladder and biliary disease

Medium: Acute pancreatitis; delayed gastric emptying and anesthesia aspiration risk; severe gastroparesis and intestinal obstruction; micronutrient and protein inadequacy; loss of facial and body fat volume and hair shedding; functional decline in older or already sarcopenic adults

Low: Non-arteritic anterior ischemic optic neuropathy, conflicted; worsening of diabetic retinopathy with rapid glucose correction; increased resting heart rate; suicidal ideation and psychiatric adverse events, conflicted; acute kidney injury from volume depletion

Speculative: Medullary thyroid carcinoma; accelerated long-term musculoskeletal aging with indefinite use

Monitoring

Marker	Target	Why
HbA1c	4.8–5.4%	Average blood sugar over ~3 months; primary efficacy marker
Fasting insulin	2–5 µIU/mL	Detects insulin resistance years before glucose rises
HOMA-IR	< 1.0	Calculated index of insulin resistance combining fasting glucose and insulin
ApoB	< 80 mg/dL (< 60 if high cardiovascular risk)	Counts all atherogenic particles; better risk marker than LDL cholesterol
Triglycerides	< 80 mg/dL	Responds quickly to visceral fat loss and carbohydrate intake
hs-CRP	< 0.5 mg/L	Systemic inflammatory tone; falls markedly on treatment
ALT	10–26 U/L (men), 8–22 U/L (women)	Tracks fatty liver improvement
Lipase	Within laboratory reference range	Pancreatic enzyme; establishes a baseline before any pancreatitis concern
eGFR with cystatin C	> 90 mL/min/1.73 m²	Kidney filtration; falls transiently with dehydration, improves long term
Urine albumin-to-creatinine ratio	< 10 mg/g	Earliest sign of kidney injury and a strong cardiovascular risk marker
Ferritin	50–150 ng/mL (with normal inflammatory markers)	Iron stores; absorption is reduced on treatment and intake falls
Vitamin B12	500–900 pg/mL	Reduced food intake and absorption concerns; deficiency causes irreversible neurological injury
25-hydroxyvitamin D	40–60 ng/mL	Nutrient status; adequate levels are associated with better treatment response
Appendicular lean mass index (DXA)	Stable or increasing over time	The direct measure of the class's most important longevity risk
Grip strength (dynamometer)	> 40 kg (men), > 25 kg (women), or stable	Cheap functional proxy for whole-body strength and an independent mortality predictor
Resting heart rate and blood pressure	< 65 bpm; < 120/80 mmHg	Blood pressure falls with weight loss and often requires medication reduction; heart rate rises slightly on treatment

Cadence: Baseline panel before starting, then 4 weeks and 12 weeks during titration, then 6 months, then every 6–12 months indefinitely for as long as the drug is continued. Body composition and strength reassessed every 6–12 months; retinal examination at 6 months applies only to those with pre-existing diabetic retinopathy.

Qualitative Assessment

Appetite and intrusive food preoccupation: reduced preoccupation with food is the earliest and most reliable indicator that the dose is working; its absence at steady state indicates an insufficient dose
Gastrointestinal tolerability: nausea, reflux, and bowel regularity, tracked through each titration step, determine whether the next escalation is appropriate
Training performance: session work capacity, load progression on major lifts, and perceived recovery — a sustained decline is the earliest functional sign of inadequate protein or excessive dose
Energy and cognitive clarity: distinguishing improvement from the flattening some users report is central to deciding whether the trade is worthwhile
Sleep quality and daytime alertness, particularly in anyone with sleep apnea, where improvement can be dramatic and may require equipment adjustment
Enjoyment of non-food activities: a specific check for the reward-blunting effect, which is easily mistaken for low mood

GLP-1 Receptor Agonists for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment