Gentle Health
Weight loss

Tirzepatide.

Of the weight-loss medicines available today, tirzepatide has produced the greatest average weight loss in clinical trials.

James Simmons, MD · Medical Director, board-certified in emergency medicine
Check my eligibility Plans from $169/month. The intake and first clinician visit are free.
Tirzepatide INJECTION SOLUTION 25 mg / mL COMPOUNDED · Rx ONLY Flip-off cap — unbroken on arrival Filled on a prescription for one named patient Every batch tested for sterility + endotoxins Ships cold-chain, 2–8 °C overnight

The medicine

Is it safe

Do I have to stay on it?

Often, yes. Many people regain substantial weight after stopping, and we do not yet know who can stop without regaining it.

  • Staying onweight loss was maintained through three years, the longest published randomised obesity follow-up
  • Stoppingabout half the weight came back within a year

Nobody has tested tapering, or stopping once the weight is off.

How it feels

Will I feel sick?

About 3 in 10 feel nauseous at some point, mostly while the dose is still going up.

Nausea
31%
Diarrhea
23%
Vomiting
12.2%
Constipation
11.7%

Out of 100 people assigned 15 mg, at any point over 72 weeks. Mostly mild to moderate; 6 in 100 stopped over side effects, against 3 in 100 on placebo.

On tirzepatide On placebo
Will it work

What are my actual odds?

lb
Lost 5% or moreof body weight
Lost 10% or moreof body weight
Lost 15% or moreof body weight
Lost 20% or moreof body weight
Lost 25% or moreof body weight

Out of 100 people assigned this dose, over 72 weeks, counting everyone who stopped early. Alongside a reduced-calorie diet and an activity target.

On tirzepatide On placebo
Is it safe

What happens if I stop?

On average, people regained about half of the weight they had lost within a year of stopping.

0% −25% −20.9% stopped here, week 36 −9.9% a year after stopping −25.3% kept taking it on the drug off the drug

Weight against starting weight. Both groups kept the same diet and activity coaching the whole time — only the drug stopped.

Will it work

Is it better than semaglutide?

For average weight loss, yes. In a head-to-head trial, people lost more weight with tirzepatide than with semaglutide.

Tirzepatide10–15 mg
−20.2%
Semaglutide1.7–2.4 mg
−13.7%

72 weeks, both titrated to the highest dose each person tolerated. Neither side was blinded.

That trial compared weight loss, not protection from heart attacks or strokes. Semaglutide has direct evidence and an FDA indication for reducing cardiovascular risk in certain adults with obesity and established cardiovascular disease.

What is it

How is it different from semaglutide (Ozempic)?

Tirzepatide acts on a second gut receptor that semaglutide does not.

Semaglutide

Ozempic, Wegovy

GLP-1 GIP

Tirzepatide

Zepbound, Mounjaro

GLP-1 GIP

GIP fully on, GLP-1 only partway

Each molecule is sold under two names: one licensed for weight, one for type 2 diabetes. Wegovy and Ozempic are the same semaglutide; Zepbound and Mounjaro are the same tirzepatide.

How it feels

Will I lose my hair?

It can cause temporary hair shedding in some people, especially during rapid weight loss.

7 in 100women
under 1 in 100men

Both on tirzepatide. On placebo it was 1.3% of women. Shedding often settles three to six months after weight stabilises; no trial participant stopped treatment because of it. Patchy hair loss is not typical and warrants medical evaluation.

Is it safe

Who cannot take this?

Do not take it if you have a personal or family history of medullary thyroid cancer or MEN2, or if you have had a serious allergic reaction to tirzepatide or its ingredients.

  • Medullary thyroid cancer, or MEN2 personal or family history — this is the boxed warning
  • Previous pancreatitis not an FDA contraindication; a history of pancreatitis requires individual medical review
  • Severe gastroparesis not recommended in the FDA label because tirzepatide slows stomach emptying
  • Type 1 diabetes tirzepatide may be used for weight loss, but insulin adjustments require specialist diabetes management
  • A serious allergic reaction to tirzepatide or to any ingredient in the formulation — an FDA contraindication
  • Pregnant, trying, or breastfeeding do not use during pregnancy; discuss when to stop before trying, or whether to use while breastfeeding
  • Already taking another GLP-1 medicine the FDA label does not recommend using them together
  • Unstable or severe mental illness needs individual review to confirm that treatment and medication use can be managed safely
Will it work

Will I lose muscle as well as fat?

Yes, some of the weight lost is lean mass, but most of the measured loss is fat.

Fat masson tirzepatide
−33.9%
Lean massmuscle, organs, water
−10.9%
Fat masson placebo
−8.2%
Lean masson placebo
−2.6%

Lean mass is not the same as muscle: it also includes organs, water and other tissue. Each bar is the change within that compartment, not its share of the weight lost.

Is it safe

Is it safe long term?

Randomised trials provide three years of follow-up in obesity and four years in type 2 diabetes. Evidence beyond that is not yet available.

In obesityblinded throughout
3 years
In diabetesvs another drug
4 years

No new common side-effect pattern appeared through three years. The four-year evidence is in people with type 2 diabetes, measured against another drug rather than placebo.

How it works

What does it do inside my body?

It reduces appetite, slows stomach emptying, and increases insulin release when blood sugar is elevated.

1 2 3 4
  • 1Brain. Appetite decreases, which can reduce how much you eat.
  • 2Stomach. Food leaves it more slowly at first, though that wears off within weeks.
  • 3Pancreas. Insulin release increases when blood sugar is elevated.
  • 4Fat tissue. In animals, fat from a meal is stored in fat cells instead of the liver.
How it works

Why do I stop feeling hungry?

Tirzepatide strengthens signals between your gut and brain that reduce appetite and help you feel satisfied with less food.

Some patients feel less hungry. Others say the constant thoughts about food become quieter. It feels different for everyone, and it does not always happen right away.

James Simmons, MD · Medical Director
Is it safe

What is the thyroid warning about?

Tirzepatide caused thyroid C-cell tumours in rats. It is unknown whether it causes them in people.

In rats

thyroid C-cell tumours, more at higher doses and longer use

In people

the risk is unknown

The label says it is not known whether this happens in people. A personal or family history of medullary thyroid cancer, or MEN2, rules you out. Report a lump in the neck, hoarseness, or trouble swallowing.

How it works

Why only one injection a week?

Tirzepatide stays in the body for about five days, which is why it only needs to be injected once a week.

Your own GLP-1made by your gut
about 2 min
Liraglutideolder GLP-1 medicine, daily
13 hrs
TirzepatideMounjaro or Zepbound, weekly
5–6 days
SemaglutideOzempic or Wegovy, weekly
about 7 days

What we dispense

Is it safe

How is the compounded medication checked?

The dispensing pharmacy uses an independent US lab to test every batch for sterility and endotoxins before shipment.

  • The pharmacyUS, state-licensed in 48 states and DC, NABP-accredited and LegitScript-certified
  • Every batchsterility and endotoxins, by an accredited US lab independent of the pharmacy
  • The active ingredientbase form, 99.4% pure on the supplier’s certificate. Compounded in the US; the ingredient itself is made abroad, at FDA-registered plants

Every trial on this page studied the branded drug. What we dispense is compounded under Section 503A: not FDA-approved, and never trialled on its own.

Pharmacy licences, accreditation records, and batch certificates are held on file and available on request.

Is it safe

Is compounded medication legal?

Yes. A licensed compounding pharmacy may prepare a patient-specific prescription when federal and state requirements are met.

  • One named patientmade on a prescription, for you, not for stock
  • Not a routine copy of the brandthe prescriber must document a patient-specific clinical difference when required

The exact requirements depend on the prescription and applicable federal and state law. Compounded medicines are not FDA-approved, and the FDA does not review them for safety, effectiveness or quality before they are dispensed.

Compounding lets me prescribe the dose a patient needs instead of limiting them to the fixed strengths available in single-dose brand pens. That flexibility can matter when someone needs to increase more slowly or stay at a lower dose.

James Simmons, MD · Medical Director
What is it

What’s in the vial — and why is glycine or B12 added?

Every vial contains tirzepatide plus either glycine or hydroxocobalamin, a form of vitamin B12. Neither additive has been shown to improve weight loss or reduce tirzepatide’s side effects.

  • Tirzepatide in every vial
  • plus one of these, depending on the prescription
  • Glycine an inactive ingredient
  • Vitamin B12 an approved medicine for other uses

Neither combination was studied in the major tirzepatide trials. Glycine appears in FDA-approved injectable products. Hydroxocobalamin is approved separately for other uses.

The supplier’s certificate reports 99.4% purity for the tirzepatide starting material. Each finished lot is tested for sterility and endotoxins.

The additives are not what makes tirzepatide work. Glycine is used in approved injectable medicines, and hydroxocobalamin is a form of vitamin B12. I go through the exact formulation with each patient so they know what is in their vial and why.

James Simmons, MD · Medical Director
Next step

Is it right for me?

A clinician can check whether tirzepatide is safe for you and whether you need it in the first place.

Complete the intake and book a visit with me. I’ll review your history and answer your questions. The intake and first visit are free.

James Simmons, MD · Medical Director
Start your intake
Dr James Simmons

Reviewed by James Simmons, MD. Medical Director, board-certified in emergency medicine. July 2026.
Educational only, not medical advice: talk to a clinician about your own history before starting or stopping anything.
Every trial cited here studied the branded drug, not the compounded medication we dispense, which is not FDA-approved and has never been trialled on its own.