What happens on the first week on semaglutide?

October 14, 2025 •

4 min read

Approximately 40% of people in clinical trials for Wegovy, a semaglutide brand, reported experiencing nausea, highlighting that mild gastrointestinal distress is a common initial experience for those starting treatment. During the first week on semaglutide, the focus is on your body's initial adjustment to a low dose, not on significant weight loss.

Quick Summary

The first week on semaglutide involves starting a low dose to allow the body to adjust. Many experience mild, temporary gastrointestinal side effects and a modest decrease in appetite, with substantial weight changes typically occurring later.

Key Points

Start Low, Adjust Gradually: The first week involves a low, 0.25 mg dose to help your body acclimate and minimize side effects before the dose is increased.
Expect Mild Side Effects: Nausea, fatigue, bloating, and other mild gastrointestinal issues are common as your body adjusts but often subside over time.
Appetite Changes Begin: You may notice subtle reductions in hunger and food cravings, feeling fuller sooner with smaller portions.
Don't Expect Rapid Weight Loss: Significant weight loss is unlikely in the first week. Focus instead on your body's adjustment and the early behavioral changes.
Hydrate and Eat Smart: To manage side effects, drink plenty of water and eat smaller, blander, low-fat meals, avoiding greasy and spicy foods.
Communicate with Your Doctor: Report severe or persistent side effects to your healthcare provider to discuss management strategies or dosage adjustments.

Your First Week on Semaglutide: A Gentle Adjustment

Starting a new medication can bring both hope and uncertainty. On the first week on semaglutide, it is essential to set realistic expectations. The initial phase is designed to be a gentle introduction, allowing your body to adapt to the medication gradually and minimizing potential side effects. The goal is not immediate, dramatic results but rather to build a foundation for long-term success.

The Purpose of the Low Starting Dose

Semaglutide is a GLP-1 receptor agonist, a class of medication that mimics the action of the naturally occurring hormone GLP-1. This hormone helps regulate appetite, slow gastric emptying, and control blood sugar. To achieve these effects without overwhelming your system, treatment starts with a very low dose, typically 0.25 mg once weekly via subcutaneous injection. This process is known as dose titration and is crucial for patient comfort and adherence.

The initial low dose allows your body’s GLP-1 receptors to become accustomed to the medication's presence. Jumping straight to a higher, more therapeutic dose would likely cause severe gastrointestinal side effects. By starting slow, your healthcare provider can monitor your response and tolerance before incrementally increasing the dose every four weeks or so.

The Week One Side Effect Experience

For many patients, the first week is marked by a mix of early effects and potential side effects as the body acclimates. These are often mild to moderate and tend to subside over time.

Gastrointestinal Symptoms

Nausea: This is one of the most commonly reported side effects when starting semaglutide. It typically occurs because the medication slows down gastric emptying, meaning food remains in the stomach longer.
Constipation or Diarrhea: The slowdown in the digestive process can lead to changes in bowel movements. While constipation may last a little longer for some, other GI symptoms like diarrhea are often temporary. Dehydration, a consequence of eating and drinking less, can also contribute to constipation.
Bloating and Gas: Feelings of fullness and abdominal discomfort are also frequently reported as the digestive system adapts.

General Well-being

Fatigue: A feeling of low energy or tiredness is common in the first week. This can be partly due to eating less, and it is crucial to stay hydrated and ensure balanced nutrition.
Headaches: Some individuals experience headaches, which are often linked to dehydration.
Appetite Changes: The first subtle sign that the medication is working is a reduction in appetite and food cravings. You may feel full faster and for longer, leading to a natural reduction in portion sizes.

How to Manage First-Week Side Effects

There are several strategies to help mitigate the common discomforts during your initial week on semaglutide:

Eat Smaller, More Frequent Meals: Overloading your stomach can worsen nausea. Small, frequent meals are gentler on the digestive system and can help manage nausea and fullness.
Stay Hydrated: Drink plenty of water throughout the day. Sipping fluids slowly can aid digestion and prevent dehydration, which helps with headaches, constipation, and overall fatigue.
Choose Bland Foods: Opt for low-fat, easy-to-digest foods like crackers, toast, rice, and lean protein. Avoid greasy, fried, and spicy foods that can exacerbate stomach upset.
Avoid Lying Down After Eating: To help with digestion and reduce reflux, stay upright for at least an hour after meals.
Incorporate Gentle Movement: Light activities like walking can help improve digestion and combat fatigue. Avoid strenuous exercise immediately after meals.
Communicate with Your Doctor: If side effects are severe or persistent, contact your healthcare provider. They can offer additional management strategies or make dosage adjustments.

First Week vs. Maintenance Phase: A Comparative Look


Feature	First Week (Initial Titration)	Maintenance Phase (Therapeutic Dose)
Dose	Low starting dose, typically 0.25 mg weekly	Higher, stable dose, up to 2.4 mg weekly for weight management
Goal	Minimize side effects and allow body to adjust	Achieve maximum therapeutic benefits for blood sugar or weight
Appetite	Subtle reduction in hunger and cravings may begin	Stronger, more consistent appetite suppression
Weight Change	Minimal to no significant weight loss; some water weight loss possible	More noticeable, steady weight loss as a result of consistent calorie deficit
Side Effects	Most common time for gastrointestinal side effects (nausea, fatigue)	Side effects typically diminish or resolve as the body adapts

Setting Expectations and Staying Patient

During the first week, you are laying the groundwork for your long-term health journey. It is crucial to remember that this medication works gradually. Do not be discouraged if the scale does not show dramatic changes immediately. The subtle shifts in appetite and cravings are signs that the medication is beginning its work. Tracking your progress, managing your diet, and staying consistent with your weekly injection are key to achieving success as you move through the dose titration schedule. By the time you reach the maintenance dose in several weeks, you will likely see more significant and sustained results.

An important aspect of this journey is recognizing that every individual’s experience is different. Factors like your metabolism, lifestyle changes, and other health conditions can influence how quickly you see results and how you experience side effects. As noted by the Mayo Clinic, patient monitoring and open communication with your provider are essential for ensuring a safe and effective treatment plan.

Conclusion

The first week on semaglutide is a period of adjustment, not a race to the finish line. By starting with a low dose, the medication aims to minimize side effects while your body acclimates. Patients can expect mild gastrointestinal symptoms like nausea and fatigue, along with the initial, subtle signs of appetite reduction. By following practical strategies to manage these side effects and maintaining open communication with your healthcare provider, you can successfully navigate this foundational week and set a positive tone for your entire treatment journey. The real benefits, both in weight management and improved blood sugar control, will emerge consistently over the following months.

Frequently Asked Questions

The typical starting dose is 0.25 mg once per week via subcutaneous injection. This low dose helps your body get used to the medication and minimizes side effects.

Yes, nausea is one of the most common side effects reported when first starting semaglutide. It often happens because the medication slows down digestion and typically lessens as your body adapts.

Significant weight loss is not expected in the first week. While some individuals may lose a few pounds due to reduced calorie intake or water loss, substantial and sustained weight loss occurs over several months as the dose is increased.

To manage constipation, focus on increasing your water and fiber intake, and try to engage in light physical activity like walking. Eating smaller, balanced meals can also help.

Most mild to moderate side effects, especially gastrointestinal ones, are temporary. They tend to be most pronounced in the first few weeks or after a dose increase, and usually resolve as your body gets used to the medication.

It is generally recommended to limit alcohol consumption while on semaglutide, as excessive drinking can exacerbate side effects and interfere with weight loss goals.

If you experience severe or persistent nausea, especially if it leads to an inability to keep fluids down, you should contact your healthcare provider immediately. This may be a sign of dehydration or another issue that requires medical attention.