What is the starting dose of retatrutide?

In clinical trials, most people started retatrutide at 2mg weekly, though some started at 4mg. We won't know the official starting dose until retatrutide is approved, but it's likely to be 2mg based on the trial data. This allows your body to adjust gradually before moving to higher strengths.

How much retatrutide should I take?

You can't take retatrutide yet as it isn't approved. Once it's licensed, the dose will depend entirely on your individual circumstances and how you respond to treatment. In clinical trials, target doses ranged from 0.5mg to 12mg weekly. Your prescriber will determine the right dose for you based on your weight loss progress, side effects, and overall health. Higher doses generally produce more weight loss but may cause more side effects.

What dosage of retatrutide is most effective?

In clinical trials, the 12mg weekly dose produced the most weight loss (up to 28.7% of body weight after 68 weeks). However, lower doses of 4mg and 8mg were still highly effective, producing significant weight loss with potentially fewer side effects. The "best" dose is the one that gives you meaningful results whilst remaining tolerable.

How is the retatrutide dosage increased?

In clinical trials, doses were increased every 4 weeks as long as people were tolerating the medication well. Once approved, your prescriber will follow the licensed protocol whilst adjusting the pace based on your individual response. If you experience side effects, they can slow down increases or keep you at your current dose longer.

How long does it take to reach your target dose?

It depends on which dose you're aiming for. In trials, people reached 4mg in 4 weeks, 8mg in 8 weeks, 9mg in 12 weeks, and 12mg in 12-16 weeks when escalating from 2mg, depending on the escalation schedule. When approved, the pace may vary based on how well you tolerate each increase. Some people need to spend longer at each dose level.

Can the dose be increased faster than every 4 weeks?

In clinical trials, doses were increased every 4 weeks. Increasing faster than this hasn't been studied and would likely increase side effects significantly. Once retatrutide is approved, your prescriber will follow evidence-based protocols to ensure your safety. If you're tolerating your current dose very well, they might suggest moving up at 4 weeks. If you're experiencing side effects, they might recommend waiting longer.

Can you change your retatrutide dose if you’re experiencing side effects?

Almost certainly, yes, once retatrutide is approved. With currently licensed weight loss medications, adjusting doses due to side effects is completely standard practice. Your prescriber can slow down your escalation schedule, keep you at your current dose longer, or step back to a lower dose temporarily if side effects become troublesome. The goal is to find a dose that's both effective and tolerable for you. However, because retatrutide isn't approved yet, there's no official guidance we can share about specific dose adjustment protocols.

What are the potential risks or side effects associated with different doses of retatrutide?

The most frequently reported side effects were digestive (nausea, diarrhoea, vomiting, and constipation), similar to other weight loss injections like Mounjaro and Wegovy. These digestive side effects occurred primarily during dose escalation, were predominantly mild to moderate in severity, and were more frequent in higher-dose groups. Importantly, side effects were partially mitigated by using a lower starting dose (2mg rather than 4mg), which is why the gradual escalation approach matters.

What are the main side effects people experience when increasing the retatrutide dose, and how can they be managed?

The most common side effects when increasing doses are nausea, diarrhoea, vomiting, and constipation. These typically occur during the first few weeks after a dose increase and often improve as your body adjusts. Strategies like avoiding trigger foods, eating less fatty or fried foods, staying hydrated, and having smaller portions more often can help. If side effects are severe or persistent, your prescriber may slow down your escalation schedule or temporarily reduce your dose. Once retatrutide is approved, your prescriber will provide specific guidance based on your symptoms.

How does retatrutide dosage vary based on specific conditions or patient factors?

We don't yet know the specific dosing adjustments that will be required once retatrutide is approved. With currently licensed weight loss medications, factors like kidney function, liver function, other medications you're taking, and how well you tolerate treatment all influence dosing decisions.Retatrutide will likely follow similar principles, with your prescriber personalising the approach based on your individual circumstances and medical history. The specific guidance on dose adjustments for different patient groups will be established when retatrutide receives regulatory approval.

Why isn't there a retatrutide dosage calculator?

Because retatrutide isn't yet approved, there are no standardised dosing guidelines. The dosing schedules used in clinical trials may differ from the final approved protocol. Once licensed, your prescriber will determine your starting dose and escalation schedule based on your individual needs, medical history, and response to treatment, not a one-size-fits-all calculator.

What is the recommended dosage for retatrutide in clinical trials?

There wasn't a single "recommended" dose in clinical trials. Researchers tested a range from 0.5mg to 12mg weekly to understand how different doses perform. The most commonly studied escalation schedules started at 2mg and increased to target doses of 4mg, 8mg, 9mg or 12mg. The 12mg dose produced the most weight loss (up to 28.7% of body weight after 68 weeks), whilst lower doses were also effective but produced less dramatic results. Once approved, the official recommended dosing will be determined by regulators based on the full trial data.

How does retatrutide dosing compare to Mounjaro or Wegovy?

All three medications follow similar principles: starting low and increasing gradually. Wegovy (semaglutide) starts at 0.25mg and increases to a maximum of 7.2mg. Mounjaro (tirzepatide) starts at 2.5mg and increases up to a maximum dose of 15mg. Based on trial data, retatrutide will likely start at 2mg and increase to 12mg.

How do I know which retatrutide dose is right for me?

You won't know until retatrutide is approved and you start treatment. Your prescriber will likely begin you on a starting dose of 2mg based on trial data, then gradually increase based on how you respond. The right dose balances effective weight loss with manageable side effects, and is determined through careful monitoring and adjustment throughout your treatment.

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Retatrutide dosage

Retatrutide dosage guide for weight loss

Retatrutide is a weekly weight loss injection currently in clinical trials. Here's what we know about the dosing schedules being tested and what to expect if it gets approved.

Medically reviewed by

Dr Earim Chaudry (MBBS), Chief Medical Officer

Updated 12th December 2025

Research-Based Guide

Retatrutide might be the most effective weight loss medication we've seen yet. In clinical trials, people lost up to 28.7% of their body weight after 68 weeks. That's significantly more than typically seen with current treatments like Wegovy or Mounjaro.

But here's the catch: retatrutide isn't approved yet. It's still undergoing clinical trials, which means we don't know exactly what doses it'll be available in once it reaches the market, or what the official dosing schedule will be.

That said, clinical research gives us a fairly clear picture of how retatrutide dosing works. Here's everything we know so far.

Key takeaways

Retatrutide isn't approved yet and isn't expected to launch in the UK until at least mid-2026
In clinical trials, target doses ranged from 0.5mg to 12mg weekly, with the most common being 4mg, 8mg, 9mg and 12mg
Different dosing schedules were tested, with most people starting at 2mg and escalating every 4 weeks
The 12mg dose produced the most weight loss (up to 28.7% after 68 weeks)
Starting at 2mg rather than 4mg helped reduce side effects during escalation

What is retatrutide?

Retatrutide is an investigational weight loss injection given once weekly. Like Wegovy and Mounjaro, it works by making you feel fuller for longer, so you naturally eat less.

What makes retatrutide different is how it works. Wegovy mimics a single hunger hormone called GLP-1, whilst Mounjaro mimics two hormones: GLP-1 and GIP. Retatrutide takes this a step further by activating three hormones: GLP-1, GIP, and glucagon.

This triple action appears to make it more potent than existing treatments, though we're yet to see head-to-head comparison studies.

FYI: Retatrutide is also being studied as a type 2 diabetes treatment, where it's shown impressive results for both blood sugar control and weight loss.

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Retatrutide dosage chart

Based on clinical trials, here's how retatrutide dosing typically works

Target dose	Starting dose	Escalation schedule	Time to target dose
0.5mg*	0.5mg	No escalation	0 weeks
1mg*	1mg	No escalation	0 weeks
4mg*	4mg	No escalation	0 weeks
4mg	2mg	2mg → 4mg	4 weeks
8mg	2mg	2mg → 4mg → 8mg	8 weeks
8mg	4mg	4mg → 8mg	4 weeks
9mg	2mg	2mg → 4mg → 6mg → 9mg	12 weeks
12mg	2mg	2mg → 4mg → 8mg → 12mg	12 weeks
12mg	2mg	2mg → 4mg → 6mg → 9mg → 12mg	16 weeks

*Fixed doses with no escalation. These lower, non-escalated doses produced modest weight loss with fewer side effects but were less effective than the escalated doses.

Important: This chart shows the dosing schedules used in research. Because retatrutide isn't approved yet, we don't know which doses will be available or what the official dosing protocol will be. Your prescriber will determine your dosing schedule based on how you respond to treatment and your tolerability once retatrutide has been approved.

Retatrutide starting dose

In clinical trials, people started retatrutide at different doses depending on their assigned treatment group.

The most common starting doses were:

2mg weekly: This was the most frequent starting point, particularly for people assigned to higher target doses (8mg or 12mg). Starting at 2mg gives your body more time to adjust before moving up to stronger doses, which helps minimise side effects.

4mg weekly: Some trial participants started at 4mg. This was used either as a fixed dose (staying at 4mg throughout) or as a faster escalation route to 8mg. Getting to a higher dose quicker leads to quicker weight loss, but may increase the risk of gastrointestinal side effects initially.

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Lower starting doses tested:

1mg weekly: Tested in the phase 2 obesity trials as a fixed dose with no escalation. This produced modest weight loss with minimal side effects.

0.5mg weekly: Tested in the type 2 diabetes trial as a fixed dose. This very low dose was well tolerated but produced less weight loss than higher doses.

The official starting dose won't be confirmed until approval, but 2mg is most likely based on trial data, as it balances effectiveness with tolerability.

How is retatrutide dose increased?

In clinical trials, retatrutide doses were increased every 4 weeks, as shown in the dosage chart above. However, this isn't set in stone.

Your prescriber may adjust the pace based on how you're responding. If you're experiencing troublesome side effects, they might keep you at your current dose for longer, or even step back to a lower dose temporarily. If you're tolerating treatment well, the escalation can proceed as planned.

Once retatrutide is approved, the official protocol may differ from what was tested in trials. Your prescriber will follow the licensed guidance whilst tailoring the approach to suit you.

Why do I need to follow a retatrutide dosing schedule?

Think about training for a marathon. You wouldn't attempt 42km on your first run. You'd gradually build up your distance over weeks and months.

Retatrutide works the same way. Following a gradual dosing schedule helps your body adapt to the medication, which significantly reduces your risk of side effects. The most common side effects when starting or increasing doses include nausea, vomiting, diarrhoea, and constipation.

This gradual approach is especially important with retatrutide because it's more potent than current weight loss medications. The triple-hormone mechanism (GLP-1, GIP, and glucagon) means it has a stronger effect on your appetite and digestive system than single or dual-hormone treatments like Wegovy or Mounjaro.

Starting on a low dose and increasing slowly gives your body time to adjust, making the side effects more manageable and treatment more tolerable overall.

What is the retatrutide maintenance dose?

During treatment: In clinical trials, people reached target doses ranging from 0.5mg to 12mg weekly, depending on their assigned group. The 12mg dose is the highest tested in trials and produced the most weight loss (up to 28.7% of body weight). Your target dose is the strength that works best for you whilst remaining tolerable.

After reaching your goal weight: We don't yet know what the maintenance strategy will be once you've achieved your weight loss goals. With currently approved medications like Wegovy and Mounjaro, some people stay on their current dose to maintain results, whilst others can reduce to a lower dose.

The approach with retatrutide will likely be similar, but we won't have official guidance until it's approved. Your prescriber will work with you to find the right dose for both achieving and maintaining your weight loss.

Can you change your retatrutide dose?

In clinical trials, participants were assigned to specific dose groups and followed set escalation schedules. But in reality, once retatrutide is approved, dosing will be much more flexible.

With currently approved weight loss medications, dose adjustments are completely normal. You'll likely increase gradually as long as you're tolerating treatment well. If you're experiencing troublesome side effects, your prescriber will likely suggest:

Staying at your current dose longer before increasing
Stepping back down to a lower dose temporarily
Slowing down the escalation schedule

The goal is to find the highest dose you can tolerate comfortably whilst still achieving meaningful weight loss. That balance looks different for everyone.

When will retatrutide be available?

Retatrutide isn't expected to launch in the UK until at least mid-2026. Phase 3 trials are still ongoing, and the medication will need regulatory approval from the MHRA (Medicines and Healthcare products Regulatory Agency) before it can be prescribed.

Once approved, we'll have clarity on:

Which doses will be available
The official dosing schedule and escalation protocol
Prescribing guidelines and eligibility criteria
NHS availability and private prescription options

Until then, the information in this guide is based on clinical trial data and may differ from the final approved product.

Your weight loss journey

Whilst retatrutide isn't available yet, there are proven weight loss medications you can access right now that could help you reach your goals, including semaglutide (Wegovy) and tirzepatide (Mounjaro).

Most weight loss treatments are prescribed based on your BMI and overall health. At Voy, we offer a comprehensive weight loss treatment plan that includes:

Monthly medication delivery to your door
Ongoing support from specialist prescribers
Personalised lifestyle guidance

Our team will work with you to find the right treatment and dose for your needs, supporting you every step of the way.

Take our short quiz to see if you're eligible.

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FAQ

FAQs about retatrutide dosage

Dr Earim Chaudry, MBBS

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DisclaimerAt Voy, we ensure that everything you read in our blog is medically reviewed and approved. However, the information provided is not meant to replace professional medical advice, diagnosis, or treatment. It should not be relied upon for specific medical advice.

References

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Aronne, Louis J et al. “Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial.” JAMA vol. 331,1 (2024): 38-48. doi:10.1001/jama.2023.24945Aronne, Louis J, et al. “Continued Treatment With Tirzepatide For Maintenance Of Weight Reduction In Adults With Obesity: The SURMOUNT-4 Randomised Clinical Trial.” JAMA, vol. 331, no. 1, 2024:38-48. https://jamanetwork.com/journals/jama/fullarticle/2812936.

^²

Doggrell, Sheila A. “Retatrutide Showing Promise In Obesity (And Type 2 Diabetes).” Expert Opinion on Investigational Drugs, vol. 32, issue 11, 2023:997-1001 https://www.tandfonline.com/doi/10.1080/13543784.2023.2283020.

^³

Jastreboff, Ania M., et al. “Triple-hormone-receptor Agonist Retatrutide For Obesity—A Phase 2 Trial.” The New England Journal of Medicine, vol. 389, no. 6, 2023:514-526 https://www.nejm.org/doi/full/10.1056/NEJMoa2301972.

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Naeem, Muhammad, et al. “Unleashing The Power Of Retatrutide: A Possible Triumph Over Obesity And Overweight: A Correspondence.” Health Science Reports, vol. 7, no. 2, 2024:e1864 https://pmc.ncbi.nlm.nih.gov/articles/PMC10844714/.

^⁵

Pasqualotto, Eric, et al. “Effects of Once-weekly Subcutaneous Retatrutide On Weight And Metabolic Markers: A Systematic Review And Meta-analysis of Randomized Controlled Trials.” Metabolism Open, vol. 24, 2024:100321 https://www.sciencedirect.com/science/article/pii/S2589936824000537?via%3Dihub.

^⁶

Rosenstock, Julio, et al. "Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA." The Lancet, vol. 402, no. 10401, 2023, pp. 529-544, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(23)01053-X/abstract.

^⁷

Eli Lilly and Company. "Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial." Eli Lilly and Company, 11 Dec. 2025, https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average.