The supplements you may need if you’re on a GLP-1

Significant weight loss is a great outcome from GLP-1 medications. That said, they can also cause some impacts to your body that aren’t as desirable, like G.I. upset, hair loss,  and losing important muscle mass and bone density, some of which might be caused by not eating enough of the nutrients your body needs. “Because your food intake is decreased while taking a GLP-1 medication, there’s a higher potential risk for micronutrient deficiency,” says Lillian Yang, R.D., CDCES, director of nutrition for Weight Watchers. While food is the best way to get nutrients, there are certain supplements to take with a GLP-1 that can help fill nutritional gaps and ease your symptoms.

Losing a considerable amount of weight, whether on a GLP-1 or not, means in addition to dropping fat, our bodies naturally shed muscle as well. “The more overall weight loss, the more muscle mass loss,” says Dr. Eduardo Grunvald, M.D., FACP, Medical Director of the University of California San Diego Center for Advanced Weight Management, though he points out that the benefits of treating obesity outweigh that risk. 

So, how are you supposed to mitigate potential muscle loss? Making lifestyle changes like adding weight-bearing exercise and fine-tuning your diet to get the protein, fiber, vitamins, and minerals you need can help. And while it’s always best to get these nutrients from food, supplements can be beneficial, especially when your appetite is tamped down. 

Here are common impacts GLP-1 users face and the supplements that can help make for a healthier weight-loss journey. 

Key Takeaways

• Because a GLP-1 shrinks your appetite, it’s easy to fall short on protein, fiber, and key micronutrients.

• Food first: supplements fill gaps; they don’t replace a protein- and fiber-rich diet.

• Supplements that may help to fill nutrition gaps on a GLP-1 are: protein, fiber (psyllium), calcium + vitamin D, and a multivitamin/B-complex (including B12).

• Probiotics may help some people with GLP-1-related digestion changes and constipation, but the evidence is still emerging.

• Your exact routine should be personalized with a doctor or dietitian — ideally guided by lab work.

Calcium
Vitamin D

A significant, scary, and common impact from losing weight is the effect it can have on your bones. “Loss of bone mass is a concern, especially with getting fractures from falls,” says Grunvald. One reason bone loss can happen is as you eat less on the medication, you may not be getting enough calcium and vitamin D from your diet.

Calcium is the building block of strong bones and teeth, but it’s also necessary for the cellular functions of your muscles and nerves. Your body is crafty — if there’s not enough calcium coming in from your diet, your body will find a source to get it…even if that source is pulling it from your own bones. This calcium cannibalism depletes bone mass and raises your risk of developing osteoporosis. That’s why everyone on a GLP-1 should be cognizant of getting calcium through foods like dairy products, sardines, dark green leafy vegetables, tofu, and fortified cereals and drinks.

Adults should aim for 1,000 mg of calcium per day. For women older than 50 and men over 70, this target increases to 1,200 mg per day. Tracking your calcium intake throughout the day can help you see how close you are to hitting these goals. If you’re falling short, consult with your primary care doctor on whether or not a calcium supplement is appropriate for you. Often a calcium supplement is recommended for:

• People with pre-existing low bone mass

• People with pre-existing low vitamin D levels (this is common — due to several complex factors, being overweight is actually a risk factor for vitamin D deficiency)

• People who have had bariatric surgery

• Women in perimenopause/menopause

• Men with low testosterone

• Anyone over 50

Many calcium supplements helpfully come paired with vitamin D, which helps your body absorb the calcium and help maintain your bone density. Vitamin D can also be found in multivitamins, if you take one. Adults should aim for 15 mcg (600 IU) of vitamin D daily between food and supplements as needed, which increases to 20 mcg (800 IU) for those older than 70 years.  Testing for vitamin D is straightforward, but checking your calcium levels, not so much. That’s because our bodies are so good at getting enough (even from our bones) that calcium levels tend to show up as normal even when there’s an issue. That’s why it’s important to make sure you’re getting enough through your diet and/or a supplement.

Whey or pea protein
Multivitamin or comprehensive B-vitamin complex

Strength/resistance training is a key way to hold onto as much muscle as possible, and so is making sure you’re getting enough protein, through sources such as fish, chicken, eggs, tofu, and legumes in your diet. The traditional way to figure out how much protein you need is to take your weight in kilograms (you can always put “X pounds in kilograms” into Google) and multiply it by 1 gram of protein. So for example, someone who weighs 200 lbs (so, 90kg) would need 90g of protein per day. But for people who are losing weight, you should be more in the range of 1.0-1.6 grams of protein per kilo, so that same 90kg person would need up to 90-144 grams of protein. With reduced intake while on a GLP-1, reaching your protein goals can be harder. To help with this, smaller, more frequently meals that incorporate protein may be recommended to consume throughout the day. If you’re still falling short of your protein target, talk to your clinician or Registered Dietitian through Weight Watchers about adding a protein supplement.

The protein boost may also help you manage another potential side effect — hair loss.

Like muscle loss, hair loss isn’t a side effect of the medication per se, but more from any kind of significant weight loss, including GLP-1s and bariatric surgery. “Hair loss usually lasts for six to 12 months and then tends to stop,” says Grunvald. “It’s not going to keep progressing until you’re bald.” 

When you’re losing weight, your body tries to slow down a lot of the processes in your body that require energy, including energy for your hair follicles. “The number one thing to reduce hair loss is to make sure that you're getting enough high-quality protein,” he says.

Along with a high-protein diet with a big variety of fruits and vegetables, you also want to make sure you’re consuming an adequate number of calories to prevent rapid hair loss. It may also help to take a good-quality multivitamin or a comprehensive vitamin B complex.

If you're adding in a protein supplement, whey protein, made from dairy, has the best bioavailability, which just means your body is better able to break it down and use it. If dairy doesn’t work for your system or you don’t eat animal products, you can opt for pea protein. Weight Watchers makes keeping track of macronutrients like protein simple. On the GLP-1 Success Program — a nutrition plan that complements your GLP-1 medication — when you track your meals in the app, it automatically tracks your protein, along with other macros like carbs, fats, fiber, and sodium. In fact, 85% of GLP-1 Success members say the nutritional guidance helps them stay on track while taking a GLP-1.*

Psyllium fiber

While nausea may be the top G.I. side effect of using a GLP-1 as your body adjusts, “the most common long-term gastrointestinal side effect I see, anecdotally, is constipation,” says Grunvald. If that’s happening for you, the first step is to make sure you’re drinking enough water. The GLP-1 Success Program guides members in drinking 64 fluid ounces (or 8 cups) of water per day. If you’re feeling constipated, try increasing this to 72 ounces per day (or adding an additional cup of water) to help soften the stool.

You also want to make sure you’re eating enough fiber; guidelines recommend that women consume at least 25 grams of fiber per day, while men should consume at least 38 grams per day. Generally, you want to get 14 grams of fiber for every 1,000 calories you eat. Yet more than 90% of women and 97% of men in the U.S. aren’t hitting those numbers. If you’re falling short of the recommendations, increase fiber gradually, one meal or snack at a time (or by ~5 grams over the course of a few days). The best way to add fiber is by making sure there are plenty of fruits and veggies, nuts, seeds, beans, legumes, and whole grains in those mini-meals you’re consuming.

If you’re unable to meet your fiber goals through food alone, talk to a clinician or Registered Dietitian about whether a fiber supplement may be a good fit for you. One recommendation they may have is psyllium husk, which is a natural fiber supplement that comes in powder form you can dissolve in water (bonus: you also get those ounces in!) or take as a tablet.

In addition to fiber, gentle movement, such as walking, can encourage natural bowel movements. Probiotics may also be helpful — more on that below.

Know those people who say “food is fuel”? They’re actually right: food is what gives you energy. So it makes sense that when you’re eating less, you may feel less peppy; fatigue is a common complaint from people on a GLP-1. Start with lifestyle changes to amp up your energy, including making sure you’re getting 7-9 hours of sleep, doing light activity like walking, and eating enough to sustain your energy (you may need to set an alarm so you don’t go more than four or five hours without eating). 

Eating less can mean you’re getting less of the nutrient B12, a nutrient that helps keep your body’s blood and nerve cells healthy and helps make your DNA, as well as helps prevent anemia, which can make you feel tired and weak. Most Americans get enough B12, but it can be harder for people who are pregnant, older, have certain autoimmune conditions, or don’t eat animal products, such as vegans, since plants don’t naturally have B12.

Food sources are the best way to get nutrients, and B12 can naturally be found in fish, meat, poultry, eggs, milk and other dairy products, clams, oysters, beef liver; some breakfast cereals and other foods are fortified with added B12.

A simple blood test can tell you your B-levels; if you’re low and don’t take medications or have conditions that interact, your provider may recommend a B12 supplement.

Remember the section above, all about how GLP-1s commonly cause constipation, and how eating enough fiber and drinking enough water are the best way to keep your system moving? That’s still true — you can’t just pop a probiotic gummy and skip out on the important stuff.

There’s good evidence that probiotics may support digestion, including regularity, and overall gut health for some people, but they haven't been studied well yet specifically for GLP-1 users. Generally, prebiotics nourish beneficial bacteria and promote their growth, and probiotics help maintain balance within the microbiome. It’s important because having an imbalance in the gut has been linked to metabolic disorders such as type 2 diabetes, obesity, and cardiovascular disease.

Before you start supplementing, remember that the best way to get beneficial probiotics is through fermented items such as yogurt, kefir, sauerkraut, kombucha, and kimchi. And as always, speak with your clinician or Registered Dietitian before starting a new supplement. 

If you’re taking a GLP-1, the above intel gives you a good idea of the supplements you may want to take. But both Grunvald and Yang agree that your specific supplement routine should be personalized and guided by a doctor or dietitian. Sadly, most people aren’t getting that guidance from an M.D. or R.D., says Grunvald. 

“Sitting down with a healthcare provider to go over your labs is ideal. Then you can see if there are deficiencies and discuss areas of concern in your life, such as being vegetarian or being in menopause; existing medical conditions; or family history that is concerning. Then together, you can make a plan of what to monitor and what foods or supplementation to prioritize,” says Yang.

Yang recommends meeting with Weight Watchers dietitians to be “your support partner through this journey and really help personalize your nutrition and supplements to ensure that you're not just getting that nutritional adequacy, but nutritional optimization.” In many cases, you’re going to need to be your own advocate to ask your prescriber about what testing and supplements make sense for you.

There are lots of positive health benefits from using a GLP-1 to eat less and lose weight, but there are also a few challenges, especially losing bone density and muscle mass. Food is the first line of defense for your body to ensure you’re getting enough fiber, protein, calcium, B12, probiotics, and vitamin D — but thankfully daily supplements are an easy way to fill in nutritional gaps if needed. Talk to your doctor or Registered Dietitian about your risk factors, blood test results, and diet to see if these supplements are right for you.

*Based on customer survey responses provided April 16-20, 2026 from 110 Core+ GLP-1 Success program members in the US who were taking GLP-1 medications