Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
If you’re considering weight loss injections, one of the biggest questions is how long you’ll need to stay on them. Research shows these medications are not short-term fixes but part of a longer treatment plan. In a clinical trial, people taking semaglutide (a common weight loss injection) stayed on it for 68 weeks and maintained significant weight loss during that time. An extension of the STEP 1 trial found that one year after stopping semaglutide treatment, participants regained about two-thirds of their lost weight, highlighting that ongoing therapy is necessary to maintain weight loss and related health benefits.
Ultimately, the duration of treatment depends on your health goals, how your body responds, and your doctor’s guidance, but evidence suggests these injections work best when used as part of a sustained plan rather than a short-term solution.
Semaglutide doesn’t cause immediate weight loss. It works gradually as your body adjusts. Clinical studies show that most people begin to notice changes in appetite and eating habits within the first 4 to 8 weeks of treatment, once the dose is slowly increased to reduce side effects.
In terms of weight loss, research from the STEP 1 trial found that participants started seeing measurable results by week 12, with more significant weight loss continuing over the following months. On average, people lost around 5% of their body weight by 3 months, and weight reduction continued to build up to 15% or more after a year, depending on adherence and lifestyle factors.
In short, semaglutide begins working on appetite fairly quickly, but meaningful weight loss typically takes a few months, and progress builds with time and consistent use.
The length of time a person may need to continue weight loss injections can vary significantly. It’s not a one-size-fits-all approach and depends on a combination of health, lifestyle, and treatment response. Below are some of the main factors that influence how long someone may need these medications:
The time required often depends on how much weight a person aims to lose. Those with larger targets may need longer treatment compared to individuals with more modest goals.
People respond differently to medications like semaglutide. Some may see noticeable results within weeks, while others progress more slowly. A slower but steady rate of progress may extend the duration of use to sustain results.
Gastrointestinal side effects, such as nausea or diarrhoea, can limit how long someone can comfortably stay on weight loss injections. For some, these symptoms are temporary; for others, they persist and may require stopping earlier than planned.
Underlying conditions, such as type 2 diabetes, cardiovascular issues, or thyroid concerns, may affect how long a person remains on treatment. In some cases, the injections are used as part of long-term management for these conditions rather than solely for weight loss.
Those who make sustainable adjustments to diet, physical activity, and daily habits may be able to reduce or discontinue injections earlier, while others who rely more heavily on medication may need longer support.
Medical supervision is a key factor. Doctors consider the balance of benefits and risks, weight loss plateaus, and health changes when advising how long a patient should continue injections.
Weight loss injections can be effective in the short to medium term, but long-term use is not without risks. Extended treatment may increase the chance of side effects and create new health challenges that require close medical monitoring.
The most common side effects of GLP-1 receptor agonists, such as semaglutide, involve the digestive system, including nausea, vomiting, diarrhoea, and constipation. While many people experience these only at the beginning of treatment, prolonged use may worsen or prolong these symptoms, sometimes leading to discontinuation.
Long-term use has been associated with concerns about thyroid health, including potential increased risk of thyroid C-cell tumours in animal studies. There is also a risk of developing pancreatitis, which is inflammation of the pancreas, and gallbladder complications such as gallstones, which have been linked to rapid or sustained weight loss.
If appetite suppression leads to very low food intake, the body may not get enough essential nutrients, including vitamins, minerals, and protein. This can lead to fatigue, weakened immunity, and loss of muscle mass over time. Studies suggest that maintaining balanced nutrition is critical to avoid these risks.
Relying solely on injections for appetite suppression can make it difficult to transition off treatment. Some patients regain weight once they stop, indicating that long-term lifestyle changes are essential for sustained results.
While weight loss injections can be effective, there are situations where continuing treatment may no longer be safe or beneficial. Stopping the injections might be necessary for health, personal, or practical reasons.
Persistent or severe side effects: Mild side effects such as nausea and constipation are common in the early stages, but if they become persistent or severe, your doctor may recommend discontinuation. Prolonged gastrointestinal distress can affect overall quality of life and nutritional status, making ongoing use unsuitable.
Plateau in weight loss results: Weight loss injections are most effective in the first months of use. Over time, some individuals may reach a plateau where weight loss slows or stops, even with continued treatment. At this stage, your doctor might advise transitioning to alternative strategies to maintain progress.
Personal or financial reasons: Long-term treatment can be costly, and not everyone chooses to continue once their initial weight goals are achieved. Some people also prefer to shift to sustainable lifestyle habits without relying on medication.
Desire to conceive or pregnancy: Weight loss injections are not recommended during pregnancy or when planning to conceive. Research indicates that medications affecting appetite and metabolism can interfere with foetal development, so discontinuation is advised if you are pregnant or planning to become pregnant.
Medical advice due to health changes: If new medical conditions arise, such as kidney or liver problems, continuing injections may no longer be safe. Regular monitoring ensures that treatment aligns with your overall health needs.
Medication interactions: Weight loss injections can sometimes interact with other prescribed medications, altering their effectiveness or causing adverse effects. If this occurs, your healthcare provider may recommend stopping the injections or adjusting treatment.
Stopping semaglutide often leads to changes in appetite and weight regulation. Since the medication works by mimicking hormones that slow digestion and reduce hunger, withdrawing it can cause appetite to return more strongly. Without ongoing treatment, many people notice their food intake increasing and the feeling of fullness fading more quickly.
Weight regain is another common outcome. A study found that participants who discontinued semaglutide regained a significant portion of the weight they had lost within a year. This highlights how the medication acts as a long-term support rather than a permanent fix.
There may also be shifts in blood sugar control, particularly in individuals using semaglutide for both type 2 diabetes and weight management. Without the medication, glucose levels may rise, which could require additional dietary adjustments or a return to other diabetes medications.
For some, stopping semaglutide is not only about physical changes but also psychological ones. The sense of control over eating habits that semaglutide provides can diminish, making it important to rely on established lifestyle habits, such as balanced eating and regular exercise, to maintain progress.
Many people notice weight gain after stopping weight loss injections, and this often comes down to how the body and habits respond once the treatment ends. Research shows that these effects are not just psychological but also physiological, which makes maintaining weight loss a real challenge without ongoing support.
While on injections like semaglutide, hunger and cravings are usually reduced, making it easier to eat less. Once the medication is stopped, appetite-regulating hormones rebound, and cravings often return stronger than before. This can make it difficult to maintain previous eating patterns. The study mentioned earlier shows that upon discontinuation, patients regained nearly all the weight they had lost about 9.7 kg on average with semaglutide.
Weight loss itself causes the body to adapt by lowering its resting metabolic rate. This means fewer calories are burned at rest compared to before. When injections are stopped, this slower metabolism persists, making it easier to regain weight even without eating more. A major NEJM study found these hormonal and metabolic adaptations, including changes in leptin, ghrelin, and energy expenditure, can last for at least a year.
Injections can create a calorie deficit, but they don’t automatically teach sustainable habits. If new eating behaviours and mindful dietary practices weren’t developed during treatment, it may be difficult to maintain weight once the injections are stopped. Evidence suggests that discontinuing medication without lifestyle interventions is strongly linked to rapid weight rebound, even when diet changes were in place.
For many, injections reduce not only appetite but also emotional triggers for eating. Once the appetite-suppressing effect disappears, old patterns of stress-driven or emotional eating can return. Broader obesity research shows that this behavioural relapse is a key factor in weight regain when medication support is removed.
Regular exercise and accountability are essential for weight maintenance. After stopping injections, many people reduce their activity levels or lose contact with their healthcare team, which can lead to a gradual regain. A study found that patients who slowly reduced semaglutide while continuing lifestyle coaching were more likely to maintain their weight, while those who stopped abruptly regained more quickly.
Weight loss injections aren’t quick fixes. They are most effective when used as part of a longer-term plan, often lasting a year or more. People who continue treatment tend to maintain weight loss, while those who stop usually regain much of it.
How long you stay on these injections depends on your health goals, how your body responds, and your doctor’s guidance. For some, they may be short-term, while for others, especially with obesity or type 2 diabetes, they may be part of a longer treatment plan.
The key point: weight loss injections can help, but they work best when combined with lasting changes in diet, activity, and lifestyle.
Want to know not just how long you’ll be on injections, but how to make them work better? Discover the safest and most effective ways to move while on weight-loss injections. Click here to learn how exercise can supercharge your results.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.