Starting a GLP-1? Side Effects, Risks & What to Know

Starting a GLP-1 medication can be an exciting step toward improving your weight, metabolic health, and overall wellness. But these are real medications, and like any medication, they come with potential side effects and risks.

The good news is that most side effects are manageable, especially when you know what to expect.

Whether you’re starting semaglutide, tirzepatide, or another GLP-1 medication, this guide covers the important stuff: how GLP-1s work, common side effects, more serious risks, and when you should contact your healthcare provider.

1. How Do GLP-1 Medications Work?

GLP-1 medications work by mimicking hormones your body already makes.

They help regulate appetite, blood sugar, and digestion. In simple terms, they can help you feel full sooner, stay full longer, and think about food less.

Semaglutide, the active ingredient in Wegovy and Ozempic, primarily targets the GLP-1 receptor. Tirzepatide, the active ingredient in Zepbound and Mounjaro, targets both GLP-1 and GIP receptors.

These medications also slow how quickly food leaves your stomach. That’s part of why they work, but it’s also responsible for many of their most common side effects.

At Flow Wellness, our goal isn’t to get you to the highest dose. It’s to find the lowest dose that gives you good results with minimal side effects.

2. What Are the Most Common GLP-1 Side Effects?

Most GLP-1 side effects involve the digestive system, especially when you’re first starting treatment or increasing your dose.

Common side effects can include:

• Nausea
• Constipation
• Diarrhea
• Heartburn or reflux
• Bloating
• Stomach discomfort
• Decreased appetite
• Feeling overly full after eating
• Fatigue

For many people, these symptoms are mild and improve as the body adjusts.

You can often reduce side effects by eating smaller meals, eating slowly, stopping when you feel full, staying hydrated, and avoiding very large, rich, greasy, or heavy meals.

Most importantly, don’t feel like you need to suffer through side effects to lose weight. Let your provider know what’s happening. Sometimes slowing down a dose increase, staying at the same dose longer, or even decreasing your dose can make a big difference.

3. What Are the More Serious Risks of GLP-1 Medications?

Serious complications are uncommon, but they’re important to know about.

Potential risks associated with GLP-1 medications can include:

• Pancreatitis
• Gallstones or gallbladder inflammation
• Severe dehydration
• Kidney problems, particularly when significant vomiting or diarrhea leads to dehydration
• Severe or persistent gastrointestinal symptoms
• Delayed stomach emptying
• Low blood sugar, particularly when GLP-1 medications are combined with certain diabetes medications
• Serious allergic reactions

GLP-1 medications also carry a boxed warning related to thyroid C-cell tumors based on animal studies. They generally should not be used in people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

This list can sound intimidating. Remember, the purpose of reviewing risks isn’t to scare you. It’s so you can recognize when something isn’t normal and get help when you need it.

4. When Should I Contact My Provider?

Some nausea, constipation, appetite reduction, or changes in bowel habits can happen while your body adjusts.

However, we want to know when symptoms become significant, persistent, or simply don’t feel right.

Contact your provider if you experience:

• Persistent or worsening nausea or vomiting
• Difficulty keeping fluids down
• Significant constipation that isn’t improving
• Persistent diarrhea
• New or significant abdominal pain
• Symptoms that are interfering with eating, drinking, sleeping, or normal activities
• Side effects that aren’t improving with your usual strategies

You don’t have to wait until something becomes severe. Often, side effects are much easier to manage when we address them early.

5. When Should I Seek Urgent Medical Care?

Some symptoms should not wait for a routine message or appointment.

Seek prompt medical evaluation for severe or persistent abdominal pain, especially if it radiates to your back or is accompanied by vomiting. This can be a symptom of pancreatitis or another condition that needs evaluation.

You should also seek urgent care for symptoms such as:

• Severe abdominal pain
• Repeated vomiting or inability to keep fluids down
• Signs of significant dehydration, such as fainting, confusion, or very little urination
• Swelling of the face, lips, tongue, or throat
• Difficulty breathing or swallowing
• Other severe or rapidly worsening symptoms

If you aren’t sure whether something can wait, it’s always reasonable to err on the side of getting evaluated.

6. Can I Take a GLP-1 During Pregnancy or Breastfeeding?

GLP-1 medications are not recommended during pregnancy and are not medications we use for weight loss while pregnant.

If you’re pregnant, think you may be pregnant, or are planning a pregnancy, let your provider know. Your medication may need to be stopped well before you start trying to conceive.

Breastfeeding also deserves a conversation with your provider because recommendations vary depending on the medication and your individual situation.

One important note for people taking tirzepatide: because it can affect the absorption of oral medications, it may temporarily make birth control pills less reliable when starting treatment or increasing your dose. Ask your provider whether you need a backup or non-oral form of contraception during these periods.

And if you become pregnant while taking a GLP-1, stop the medication and contact your healthcare provider.

7. What Should I Know Before Surgery, Anesthesia, or a Procedure?

Because GLP-1 medications can slow stomach emptying, they’re important to mention before surgery, anesthesia, sedation, or certain procedures.

Having food remaining in the stomach during anesthesia or deep sedation can increase the risk of aspiration, which means stomach contents entering the lungs.

Recommendations about whether to continue or temporarily hold a GLP-1 have changed over time and aren’t exactly the same for every patient or procedure.

So don’t guess.

Tell your surgeon, anesthesiologist, dentist, or procedural team that you take a GLP-1 medication and follow their instructions about when to take your last dose.

This is especially important if you’ve recently increased your dose or are experiencing nausea, vomiting, significant constipation, bloating, or a feeling that food is sitting in your stomach for a long time.

8. What Should I Know About Compounded GLP-1 Medications?

Some Flow Wellness patients use compounded GLP-1 medications when clinically appropriate.

A compounded medication is prepared by a licensed compounding pharmacy for an individual patient.

That doesn’t mean all compounded medications are the same. The pharmacy matters. The formulation matters. Storage and handling matter. And appropriate medical oversight matters.

We take medication sourcing seriously and work with appropriately licensed compounding pharmacies. Your provider will discuss whether an FDA-approved or compounded medication is appropriate based on your individual circumstances and current availability.

Flow Tip: Be cautious with extremely inexpensive GLP-1 medications sold online without meaningful medical oversight. Know what medication you’re receiving, where it was compounded, its concentration, and how long the vial is intended to be used.

9. How Should I Store and Use My GLP-1 Medication?

Storage instructions depend on the exact medication and formulation you’re using, so always follow the instructions that come with your prescription.

If you’re using a compounded medication in a vial, your prescription label will tell you how much to inject and how to store it. Many compounded injectable medications require refrigeration.

A few basics:

• Check the medication label before every injection.
• Follow your prescribed dose rather than copying someone else’s dose or number of syringe units.
• Use a new needle and syringe for every injection.
• Don’t share medication, pens, needles, or syringes.
• Follow your pharmacy’s storage and beyond-use instructions.
• Contact us if your medication looks unusual, has been stored incorrectly, or you’re unsure how much to inject.

Units on a syringe are not the same thing as milligrams of medication. Concentrations can vary between pharmacies and prescriptions, so never assume that your friend’s “20 units” is the same dose as yours. Learn more Medication Dosage: Concentration, Quantity, and Units Injected

10. What Happens If I Miss a Dose?

First, don’t panic. Missing a dose does not erase your progress.

What you should do next depends on which GLP-1 you’re taking, how long it’s been since your scheduled dose, and how long you’ve been off medication.

Don’t automatically double your next dose to make up for a missed injection.

If you’ve been off your medication for an extended period, contact your provider before restarting. After a longer break, jumping straight back to your previous dose may cause significantly more nausea or other gastrointestinal side effects.

When in doubt, ask us! We’d much rather help you restart appropriately than have you spend the weekend regretting an ambitious injection.

11. Why Doesn’t Flow Automatically Increase My Dose?

Because the goal isn’t to win a race to the maximum dose.

We want to find the lowest effective dose that helps control appetite, supports your health goals, and causes minimal side effects.

If you’re losing fat, maintaining muscle, feeling good, and your appetite is well controlled, there is probably no reason to increase your medication simply because a higher dose exists.

This is also why we don’t make dosing decisions based on the scale alone.

We look at the whole picture, including:

• Weight and body composition
• Appetite and food noise
• Muscle mass
• Visceral fat
• Side effects
• Energy
• Strength and activity
• Metabolic health
• Your goals and preferences

Sometimes the right next dose is higher. Sometimes it’s exactly where you are. And sometimes it’s lower.

12. How Do I Protect Muscle While Losing Weight?

Losing weight and losing fat are not exactly the same thing.

When you lose weight, some muscle can be lost along with fat. That’s why we care about body composition, not just the number on the scale.

Protecting muscle becomes especially important when your appetite is significantly reduced.

Focus on:

• Getting enough protein
• Resistance or strength training regularly
• Eating enough overall nutrition
• Staying physically active
• Avoiding unnecessarily rapid weight loss
• Tracking body composition when possible

For many of our patients, we aim for at least 80 grams or more of protein per day, although your individual needs may be higher.

Muscle isn’t just about appearance. It supports strength, mobility, metabolism, bone health, and your ability to stay active as you get older.

The goal isn’t simply to weigh less.

It’s to become healthier while you do it.

13. What About Hair Loss on a GLP-1?

Hair shedding can happen during significant or rapid weight loss, whether or not a GLP-1 medication is involved.

Often, the medication isn’t directly damaging the hair. Instead, rapid weight loss, reduced calorie intake, inadequate protein, nutritional deficiencies, illness, stress, and hormonal changes can temporarily shift more hair follicles into a shedding phase.

If you’re noticing increased hair loss, tell us.

Depending on your situation, we may look at your rate of weight loss, protein intake, nutrition, iron or ferritin, thyroid function, hormones, medications, and other possible causes.

This is another reason we don’t believe faster weight loss is always better.

We want results you can actually feel good about.

14. What If My Weight Loss Slows Down?

It probably will.

Weight loss is rarely a straight line, and slowing or plateaus are especially common after you’ve been on treatment for several months.

That does not mean your medication has stopped working.

As your body gets smaller, it requires less energy. Appetite can change. Your body adapts. And the dramatic losses that sometimes happen early in treatment naturally become harder to maintain.

This is when we look beyond the scale.

Are you still losing body fat? Maintaining muscle? Getting stronger? Feeling better? Has your visceral fat improved? Are your blood pressure, cholesterol, or blood sugar moving in the right direction?

Sometimes a plateau means we adjust medication. Other times we focus on nutrition, protein, resistance training, sleep, stress, or another part of your health.

15. What Happens When I Reach My Goal?

Reaching your goal isn’t the end of treatment. It’s when the strategy changes.

Obesity and weight regulation are complex, and many people regain weight after stopping GLP-1 treatment completely. That doesn’t mean everyone needs the same medication or dose forever.

At Flow Wellness, we create an individualized maintenance plan based on your body composition, appetite, metabolic health, lifestyle, medication response, and goals.

That might include continuing your current dose, reducing your dose, spacing treatment differently when clinically appropriate, transitioning to another strategy, or eventually trying to discontinue medication.

Some of our patients do well on very small, individualized doses, often casually referred to as “microdosing.”

The goal is to use the least medication necessary to maintain the health improvements you’ve worked hard to achieve.

Your GLP-1 Should Be Part of a Bigger Plan

GLP-1 medications can be incredibly useful tools, but the medication is only one part of what we’re working on.

At Flow Wellness, we’re looking at where you want to be years from now, not just what the scale says next week.

That means protecting muscle, improving body composition, supporting metabolic and cardiovascular health, building habits you can actually maintain, and adjusting your treatment as your body and goals change.