Drug: GLP-1-medicijnen

What It Is

GLP-1 medicines are engineered copies of a gut hormone the body releases after eating, one that curbs appetite. The best known is semaglutide, sold as Ozempic and Rybelsus for type 2 diabetes and as Wegovy for weight management. Tirzepatide, sold as Mounjaro for diabetes and Zepbound for weight, acts on two gut-hormone receptors at once. Most are given as a weekly injection, and an oral form exists. They began as diabetes treatments and turned out to produce weight loss and heart protection well beyond earlier diabetes drugs.

These drugs act on the biology of appetite. Hunger and fullness are controlled by hormones. In many people these hold body weight around a higher set point, making weight hard to lose and easy to regain. Much of that pressure is manufactured. Ultra-processed foods engineered around fat, sugar, and salt supply more than half of the calories in the average American adult's diet. That food environment is a driver of the weight these drugs treat. The GLP-1 drugs act on the appetite system directly. That is why they produce weight loss diet and exercise alone rarely reach.

What It Does

The largest and most certain effect is weight. In large randomized trials semaglutide takes off about 15% of body weight, tirzepatide closer to a fifth, more than any drug before them. In type 2 diabetes they also lower long-term blood sugar (HbA1c) by around two percentage points.

Over years, in people with diabetes or established heart disease, these drugs prevent major cardiovascular events, slow kidney disease, and lower the chance of dying from any cause. Semaglutide cut major cardiovascular events by about a fifth in people who were overweight and had heart disease but no diabetes. It was the first GLP-1 drug shown to do so without diabetes in the picture.

At the approved weekly dose, semaglutide now improves both the inflammation and the early scarring of metabolic (MASH) liver disease. Trials are extending into obstructive sleep apnea and other conditions.

The Research & Studies

Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.

Weight And Fat Loss

Semaglutide took off about 15% of body weight in obesityStrong

In plain terms

People with obesity lost about 15% of their body weight over roughly sixteen months on weekly semaglutide, compared with about 2% on a dummy injection, and most lost at least 5%.

In detail

STEP 1 was a 68-week randomized, double-blind trial in 1,961 adults with a BMI of 30 or more (or 27 with a weight-related condition) and no diabetes, both arms receiving lifestyle counseling. Mean change in body weight was -14.9% with semaglutide 2.4 mg weekly versus -2.4% with placebo, a treatment difference of 12.4 percentage points. 86.4% of the semaglutide group lost at least 5% of body weight, 69.1% lost at least 10%, and 50.5% lost at least 15%. Weight fell steadily over the titration period and then plateaued.

The study · 1

Wilding et al., once-weekly semaglutide in adults with overweight or obesity (STEP 1) · N Engl J Med 2021;384:989-1002

Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.

Tirzepatide took off up to 20.9% of body weight at its top doseStrong

In plain terms

On the highest dose of tirzepatide, people with obesity lost about a fifth of their body weight over eighteen months, more than the roughly 15% seen with semaglutide.

In detail

SURMOUNT-1 was a 72-week randomized, double-blind trial in 2,539 adults with obesity (or overweight with a complication) and no diabetes. Mean weight change was -15.0%, -19.5% and -20.9% at tirzepatide 5, 10 and 15 mg weekly versus -3.1% on placebo. Tirzepatide is a dual agonist acting on both the GLP-1 and the GIP receptor, and 57% of those on the 15 mg dose (50% at 10 mg) lost at least a fifth of their body weight.

The study · 1

Jastreboff et al., tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) · N Engl J Med 2022;387:205-216

Ongeveer twee derde van het verloren gewicht keert binnen een jaar na stoppen terugModerate · risk

In plain terms

Na het stoppen van semaglutide kwamen mensen binnen een jaar ongeveer twee derde van het verloren gewicht terug, en hun bloeddruk en bloedsuiker dreven terug naar waar ze begonnen.

In detail

Deze verlengingsstudie volgde 327 deelnemers van STEP 1 een jaar nadat zowel semaglutide als leefstijlinterventie op week 68 waren ingetrokken. Deelnemers herwonnen ongeveer twee derde (11.6 procentpunten van de 17.3% verloren) van hun eerdere gewichtsverlies tegen week 120, en cardiometabolische verbeteringen inclusief bloeddruk en geglycosyleerd hemoglobine keerden evenzo terug naar uitgangswaarden. Het patroon weerspiegelt dat het geneesmiddel alleen werkt terwijl het wordt ingenomen en het setpoint van het lichaam niet herinstelt.

How to use it

Omdat het effect afhangt van het innemen van het geneesmiddel, plan van meet af aan voor de lange termijn, inclusief kosten en de gewoonten die het resultaat ondersteunen.

The study · 1

Wilding et al., weight regain and cardiometabolic effects after withdrawal of semaglutide, the STEP 1 trial extension · Diabetes Obes Metab 2022;24:1553-1564

Blood Sugar

Both drugs cut HbA1c about 2 percentage points in type 2 diabetesStrong

In plain terms

In type 2 diabetes, both drugs lowered long-term blood sugar (HbA1c) by around two percentage points, a large drop, with tirzepatide slightly ahead of semaglutide.

In detail

SURPASS-2 was a 40-week open-label randomized trial in 1,879 adults with type 2 diabetes inadequately controlled on metformin (mean baseline HbA1c 8.28%). HbA1c fell by 2.01, 2.24 and 2.30 percentage points on tirzepatide 5, 10 and 15 mg and by 1.86 on semaglutide 1 mg. Tirzepatide was non-inferior and superior to semaglutide at all three doses, and produced greater weight loss as well.

The study · 1

Frias et al., tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2) · N Engl J Med 2021;385:503-515

Heart And Vascular

Semaglutide cut major cardiovascular events 20% in obesity without diabetesStrong

In plain terms

In people who were overweight and already had heart disease but not diabetes, semaglutide lowered the rate of heart attacks, strokes and cardiovascular deaths by about a fifth over three years.

In detail

SELECT was a randomized, double-blind trial in 17,604 adults aged 45 or over who were overweight or obese and had established cardiovascular disease but not diabetes. Over a mean follow-up of 39.8 months, the primary composite endpoint occurred in 6.5% on semaglutide 2.4 mg versus 8.0% on placebo (HR 0.80, 95% CI 0.72 to 0.90). This was the first trial to show a GLP-1 drug prevents cardiovascular events in people without diabetes, and the benefit appeared partly separable from the weight lost.

The study · 1

Lincoff et al., semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT) · N Engl J Med 2023;389:2221-2232

Semaglutide cut major cardiovascular events 26% in high-risk type 2 diabetesModerate

In plain terms

In people with type 2 diabetes at high heart risk, semaglutide lowered heart attacks, strokes and cardiovascular deaths by about a quarter over two years.

In detail

SUSTAIN-6 was a 104-week randomized, double-blind pre-approval cardiovascular safety trial in 3,297 adults with type 2 diabetes at high cardiovascular risk. The primary composite occurred in 6.6% on semaglutide versus 8.9% on placebo (HR 0.74, 95% CI 0.58 to 0.95), driven mainly by a reduction in nonfatal stroke and nonfatal heart attack, not cardiovascular death.

The study · 1

Marso et al., semaglutide and cardiovascular outcomes in patients with type 2 diabetes (SUSTAIN-6) · N Engl J Med 2016;375:1834-1844

Longevity And Mortality

GLP-1 drugs lowered death from any cause 12% in type 2 diabetesStrong

In plain terms

Pooling the big diabetes heart-outcome trials, these drugs lowered the chance of dying from any cause by about 12%, and cut heart and kidney events as well.

In detail

Deze systematische review en meta-analyse poolde 8 gerandomiseerde cardiovasculaire-uitkomsttrials van GLP-1-receptoragonisten bij 60,080 volwassenen met type 2-diabetes. Sterfte door alle oorzaken werd met 12% verminderd (HR 0.88, 95%-BI 0.82 tot 0.94), het samengestelde driecomponentige ernstige nadelige cardiovasculaire voorval met 14% (HR 0.86), en een samengesteld nieruitkomst met 21% (HR 0.79). Effecten waren grotendeels consistent over de individuele geneesmiddelen in de klasse.

The study · 1

Sattar et al., cardiovascular, mortality, and kidney outcomes with GLP-1 receptor agonists in type 2 diabetes, systematic review and meta-analysis · Lancet Diabetes Endocrinol 2021;9:653-662

Digestion

Misselijkheid bereikte vroeg ongeveer 44%, en ongeveer 7% stopte het geneesmiddelStrong · risk

In plain terms

Misselijkheid is de meest voorkomende bijwerking, die vroeg bijna de helft van de mensen bereikt, samen met diarree, braken en constipatie. Ze zijn meestal mild tot matig en nemen af naarmate het lichaam zich aanpast, hoewel sommige mensen ermee stoppen.

In detail

In de STEP 1-obesitastrial (1,961 volwassenen, 68 weken) waren gastro-intestinale aandoeningen de meest voorkomende bijwerkingen met semaglutide 2.4 mg: misselijkheid bij ongeveer 44% versus 18% op placebo, met diarree, braken en constipatie ook verhoogd. De meeste voorvallen waren voorbijgaand en mild tot matig, geconcentreerd in de dosisescalatieperiode. Staking vanwege bijwerkingen was ongeveer 7% bij semaglutide versus 3% bij placebo, voornamelijk gedreven door gastro-intestinale symptomen.

How to use it

Het langzaam verhogen van de dosis, kleinere maaltijden eten en stoppen als je vol bent, vermindert de symptomen; ernstige of aanhoudende symptomen zijn een reden om de voorschrijver de voortgang te laten vertragen of te pauzeren.

The study · 1

Wilding et al., once-weekly semaglutide in adults with overweight or obesity (STEP 1), adverse events · N Engl J Med 2021;384:989-1002

Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.

Semaglutide 2.4 mg verbeterde leverfibrose bij 36.8% versus 22.4% en loste steatohepatitis op bij 62.9% versus 34.3%Moderate

In plain terms

Bij mensen met de inflammatoire vorm van leververvetting en vroege littekenvorming klaarde semaglutide bij de goedgekeurde wekelijkse dosis van 2.4 mg de ontsteking bij ongeveer 63% versus 34% op placebo en verbeterde de littekenvorming bij 36.8% versus 22.4%. Een eerdere trial bij een lagere dagelijkse dosis had de ontsteking geklaard maar de littekenvorming niet beïnvloed.

In detail

De fase-3 ESSENCE-trial randomiseerde 1,197 volwassenen met biopsie-gedefinieerde metabole-disfunctie-geassocieerde steatohepatitis (MASH) en leverfibrose stadium F2 of F3 in een 2:1-verhouding naar eenmaal wekelijks semaglutide 2.4 mg of placebo. Bij de vooraf gespecificeerde week-72-interimanalyse van de eerste 800 patiënten trad vermindering van leverfibrose zonder verslechtering van steatohepatitis op bij 36.8% op semaglutide versus 22.4% op placebo, en resolutie van steatohepatitis zonder verslechtering van fibrose bij 62.9% versus 34.3%, beide P<0.001; 32.7% bereikte beide. Een eerdere 72-weekse fase-2-trial bij 320 volwassenen, met een lagere dagelijkse dosis van 0.4 mg, had steatohepatitis opgelost bij 59% versus 17% maar had het fibrosestadium niet significant verbeterd.

How to use it

Bij de goedgekeurde wekelijkse dosis verbetert semaglutide nu zowel de ontsteking als de vroege littekenvorming van MASH, dus het levervoordeel is een reden om het te overwegen wanneer MASH samengaat met obesitas of type 2-diabetes, onder begeleiding van een specialist. Of het cirrose en de complicaties ervan voorkomt, wordt nog getest.

The studies · 2

Semaglutide in MASH with fibrosis, ESSENCE, NEJM 2025 · N Engl J Med 2025

Newsome et al., a placebo-controlled trial of subcutaneous semaglutide in nonalcoholic steatohepatitis · N Engl J Med 2021;384:1113-1124

Kidney Disease

Semaglutide verlaagde grote niergebeurtenissen met 24% bij diabetische nierziekteModerate

In plain terms

Bij mensen met type 2-diabetes en bestaande nierziekte verlaagde semaglutide de kans op nierfalen en grote nierverlies met ongeveer een kwart.

In detail

FLOW was een gerandomiseerde, dubbelblinde trial bij 3,533 volwassenen met type 2-diabetes en chronische nierziekte. Het primaire samengestelde eindpunt van grote nierziekte-gebeurtenissen (begin van nierfalen, een aanhoudende daling van eGFR van ten minste 50%, of dood door nier- of cardiovasculaire oorzaken) werd met 24% verminderd met semaglutide (HR 0.76, 95%-BI 0.66 tot 0.88). De trial werd vroeg gestopt vanwege effectiviteit, en semaglutide verminderde ook cardiovasculaire voorvallen en dood door alle oorzaken.

The study · 1

Perkovic et al., effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW) · N Engl J Med 2024;391:109-121

Muscle And Strength

Ongeveer een kwart van het verloren gewicht is spier, niet vetModerate · risk

In plain terms

Ongeveer een kwart van het gewicht verloren bij deze geneesmiddelen is spier en ander mager weefsel, niet vet, vergelijkbaar met gewichtsverlies door andere middelen. Het lichaam werd niet proportioneel minder gespierd, dus de zorg is het totale verloren spierweefsel, wat meer telt naarmate je ouder wordt.

In detail

Deze meta-analyse poolde 22 gerandomiseerde trials (2,258 deelnemers) met lichaamssamenstelling-meting. GLP-1-receptoragonisten verlaagden het totale lichaamsgewicht met ongeveer 7.8 lb (3.55 kg), waarbij mager weefsel verantwoordelijk was voor ongeveer 25% van het verlies. Relatieve magere massa, uitgedrukt als procentuele verandering van de uitgangswaarde, was niet aangetast, wat aantoont dat het lichaam niet proportioneel minder gespierd werd. Liraglutide was het enige middel dat gewicht verlaagde zonder de magere massa significant te verminderen, terwijl semaglutide en tirzepatide het meest effectief waren voor vetverlies en onder de minst effectieve voor het bewaren van magere massa.

How to use it

Voldoende eiwit en regelmatige krachttraining zijn de bewezen hefbomen om spier te beschermen tijdens gewichtsverlies, wat de reden is waarom ze naast het geneesmiddel horen, niet erna, vooral voor oudere volwassenen.

The study · 1

Effect of GLP-1 receptor agonists and co-agonists on body composition, network meta-analysis · Metabolism 2025

How It Works

These drugs work on three linked systems at once. In the brain, they act on appetite centers to reduce hunger and the urge to eat between meals. In the stomach, they slow how fast a meal empties, so fullness comes sooner and lasts longer and the rise in blood sugar after eating is gentler. In the pancreas, they raise insulin release only when blood sugar is high. That is why, used alone, they rarely push it too low. For the metabolic system underneath all of this, see insulin and glucose handling.

Anatomy of the Practice

1The gut hormone they copy

The gut releases GLP-1 after eating, then breaks it down within minutes. These drugs copy that hormone in a form that resists breakdown, so a single weekly injection keeps the signal going for days. Because they are proteins, they break down if swallowed, so most are injected. The dose is raised in steps over several weeks to let the gut adjust.

2The two-receptor drugs

Tirzepatide adds a second target, the GIP receptor, alongside GLP-1. GIP, another gut hormone, helps drive insulin release and fat storage. Acting on both receptors appears to produce more weight loss than GLP-1 alone. That is the leading explanation for tirzepatide's larger effect.

3Why appetite falls

In trials that measured energy use, the weight loss comes almost entirely from eating less, with little change in how many calories the body burns. Slower stomach emptying means food stays longer and fullness comes sooner. Brain signaling lowers hunger and the urge to eat between meals. Less food goes in, and the body draws on its own fat stores.

The Trade-offs and What Is Not Yet Known

Gut side effects are the most common cost of these drugs. Raising the dose slowly is the main lever that keeps them manageable, though a minority stop the drug because of them.

Some of the loss is lean muscle, and older adults start with less to spare, so how much you lose matters more with age. Enough protein and regular resistance training are the two levers shown to protect it: see protein and muscle and resistance training.

The effect lasts only while the drug is taken. The weight and the metabolic gains return when the drug stops, so these are treatment for an ongoing condition, planned over years.

Some things are not settled. The longest trials run about three to four years, so the open questions are all about the long run:

• Decade-scale safety is not yet established.
• Most of the weight and heart evidence comes from people who were obese or already at high cardiovascular risk, so the benefit in lower-risk, general use is less certain.

Using Them Well

Starting a GLP-1 drug is a decision to make with a prescriber. What to bring to that conversation, and how to get the most from the treatment if it fits:

1

Build on the basics firstFree to lowModerate

Whole food, steady activity, sleep, and enough protein are the foundation of weight and metabolic health. The drug builds on these habits, and they stay whether or not you go on the medicine. Keep them from the start.

2

Decide it with a prescriberVariesEasy

Whether one fits depends on your weight, your blood sugar, your heart and kidney health, and your other conditions and medicines. A clinician sets the starting dose, raises it in steps, and monitors how you respond.

3

Ease the gut effects by going slowFreeEasy

Raising the dose slowly is what keeps gut symptoms manageable. Eating smaller meals, slowing down, and stopping when full tend to help. If symptoms are severe or lasting, the prescriber can slow the pace or pause the increase.

4

Plan for the long term from the startVariesModerate

Think from the outset about the plan over years, and the eating and training habits that support the result whether or not you stay on the drug.

Go Deeper

• Type 2 diabetes: where these drugs change long-term outcomes, next to the lifestyle levers that matter most in early disease.
• Weight and metabolic health: the whole picture of fat loss, where these drugs sit after the basics of training, protein and whole food.
• Peptides: the wider peptide market, where the GLP-1 drugs are the approved, trial-tested end.
• Protein and muscle: the daily protein target that preserves lean mass while you lose fat.
• Resistance training: the minimum effective dose of resistance work, and why it holds muscle during weight loss.

The Chinese Medicine View

These are modern drugs, isolated and engineered in the last few decades, so there is no classical Chinese entry for any of them. No historical text assigns a channel, a temperature or a flavor to a GLP-1 medicine, and no traditional formula contains one.

These drugs act on functions Chinese medicine has always reasoned about. The Spleen, in this framework, governs the transformation and transport of food into usable substance. The Spleen and Stomach are the two organs it reads as the seat of appetite, fullness and digestion. When that function is weak, the tradition describes food and fluid failing to move and transform, gathering instead as Dampness and Phlegm. Those patterns are often laid over the modern picture of carrying excess weight with a sluggish metabolism. A drug that slows the stomach, reduces appetite and shifts how the body handles food is, in a loose sense, acting on those same functions.

The tradition would also draw a distinction. The drug reduces appetite. It does not, in this framework, strengthen the Spleen function itself. Chinese medicine reads three signs (persistent poor appetite, early fullness and fatigue after eating) as a depleted Spleen. In this framework those signs are a depletion to correct. So the drug addresses the symptom, appetite, while the tradition's own aim, a Spleen that transforms food well on its own, is left untouched. That gap is one reading of why the effect fades once the drug is stopped.

Cautions For These Medications

Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.

GLP-1-middelen verhoogden galblaas- en galwegziekte met ongeveer een derde

Deze systematische review en meta-analyse poolde 76 gerandomiseerde onderzoeken (103,371 patiënten, gemiddelde leeftijd 57.8, 40.5% vrouwen). Randomisering naar een GLP-1-receptoragonist hing samen met een 37% hoger risico op galblaas- of galwegziekte (RR 1.37, 95%-BI 1.23 tot 1.52), waaronder cholelithiasis (RR 1.27) en cholecystitis (RR 1.36). Het risico was hoger bij hogere doses (RR 1.56) en bij langere behandeling, en was het grootst in gewichtsverliesstudie (RR 2.29) versus diabetesstudies (RR 1.27), wat consistent is met snel gewichtsverlies als onderdeel van het mechanisme. De onderzoeken rapporteerden relatieve risico's zonder een duidelijk absoluut cijfer.He et al., association of GLP-1 receptor agonist use with risk of gallbladder and biliary diseases, systematic review and meta-analysis of randomized clinical trials

These are prescription medicines, and the starting decision sits with a clinician

Whether one fits, at what dose, and how fast to raise it depends on your full picture: blood sugar, heart and kidney health, other conditions and other medicines. Start, change, or stop one only with your prescriber. Compounded or gray-market versions sold outside a pharmacy carry no check on what is actually in the vial, and dosing errors with them have sent people to the hospital.

Not in pregnancy or when trying to conceive

These drugs are not recommended in pregnancy, and guidance is to stop them well before a planned pregnancy because they clear slowly. Anyone who could become pregnant should discuss contraception and timing with a prescriber. Because early appetite suppression can reduce how well the pill is absorbed, a backup method is often advised. Rapid weight loss around conception is itself a reason for medical guidance.

Gallbladder, biliary and pancreas

Across randomized trials these drugs raise the risk of gallbladder and biliary disease by about a third. The risk is higher at larger doses and in weight-loss use, partly a consequence of rapid weight loss itself. Pancreatitis has been reported as well. Severe, persistent abdominal pain, especially with vomiting, is a reason to seek care promptly; do not wait it out.

A thyroid contraindication for some families

In rodent studies these drugs caused thyroid C-cell tumors. It has not been shown in people. Still, the drugs are contraindicated for anyone with a personal or family history of medullary thyroid carcinoma, or the genetic syndrome MEN 2. Raise that history before starting.

Severe or lasting gut symptoms

Nausea, vomiting, diarrhea and constipation are the usual side effects and are most common in the first weeks and while the dose climbs. For most people they are mild to moderate and ease with time and a slower increase. If they are severe or lead to dehydration, the prescriber should adjust the plan.

Tell your team before surgery or an endoscopy

Because these drugs slow how fast the stomach empties, food can remain longer than expected. That raises the risk of breathing stomach contents into the lungs under sedation or general anesthesia. Anesthesiology guidance now asks that your prescriber and procedure team know you take one. They can then hold a dose or take extra precautions before surgery or an endoscopy. Do not stop on your own, but do make sure they know.

Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.

Common Questions

How much weight do people lose on GLP-1 medicines?

Averaged across the big trials, adults with obesity lost about 15% of body weight over 16 months on weekly semaglutide, against about 2% on a dummy injection. Tirzepatide's highest dose reached about a fifth. These are averages; individual results vary widely, and the loss builds gradually as the dose climbs. Those figures come from people without diabetes, in type 2 diabetes the weight loss tends to run somewhat smaller.

Do these drugs help the heart, or only weight?

They do more than trim weight. The cardiovascular benefit (fewer heart attacks, strokes, and cardiovascular deaths over roughly three years) is larger than weight loss alone would predict. That points to effects on blood vessels and inflammation beyond the pounds lost. In type 2 diabetes, semaglutide lowered cardiovascular events as well. That combination of weight, blood-sugar, and heart benefit is why these drugs are used for more than weight loss.

What happens if I stop taking one?

In the extension of the semaglutide weight trial, people regained about two-thirds of what they had lost within a year of stopping.

Blood pressure and blood-sugar markers drifted back toward where they started. Building steady eating and training habits alongside the drug holds on to more of the result if the drug is ever stopped.

Will I lose muscle on a GLP-1 medicine?

Some. When the body loses a large amount of weight, part of it is muscle. Pooled trial data put that share at about a quarter of the total, similar to weight loss by any means. Lean mass fell in step with total weight, the share of the body that is muscle stayed about the same.

Are GLP-1 medicines a cure for type 2 diabetes?

They treat type 2 diabetes powerfully without curing it. Blood sugar falls sharply on both drugs, but it tends to rise again if the drug stops. Early type 2 diabetes can sometimes reach remission through weight loss itself. These drugs drive that weight loss but do not, on their own, make the remission permanent. They work best inside care that also uses the lifestyle levers on the type 2 diabetes page.

They are expensive. Are compounded or online versions the same thing?

Not reliably. Brand-name GLP-1 drugs are costly, and coverage varies widely. That gap has driven a large market in compounded and online versions. Those are not held to the same manufacturing checks, so what is in them is not guaranteed. If cost is the barrier, a prescriber can walk through approved brands like Wegovy or Zepbound and any access programs.