The 7 supplements you may need if you’re on a GLP-1

When people talk about side effects of GLP-1s, the ones that get the most air time are uncomfortable G.I. symptoms. But these meds may be causing side effects in your body that are less obvious — namely, losing important muscle mass and bone density that could raise your risk of breaking a bone from a simple fall.

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 Eduardo Grunvald, MD, 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 those risks? Lifestyle changes. Adding weight-bearing exercise to your routine and fine-tuning your diet to get the protein, vitamins, and minerals you need can help. And while it’s always best to get these nutrients from food, supplements can help fill in the gaps, especially when your appetite is tamped down.

“It is possible that someone using GLP-1 medications could be meeting the recommended intake for these nutrients. But because your food intake is decreased while taking a GLP-1 medication, there’s a higher potential risk for micronutrient deficiency,” says Michelle Cardel, MS, RD, Ph.D., chief nutrition officer at WeightWatchers.

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

Supplements for bone health

Calcium
Vitamin D

The most significant and scary (and common) impact from losing weight is the consequence it can have on your bones. “Loss of bone mass is a concern, especially with getting fractures from falls,” says Grunvald. Why does bone loss happen? 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, nerves, and glands. 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.

Most people on a GLP-1 will need to take a daily 500 mg calcium supplement, says Cardel. It is especially 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 maintain your bone density. (Check how much vitamin D you’re getting in your multivitamin as well if you take one — more on that below). 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.

Supplements for muscle (and hair) loss

Multivitamin
Whey or pea protein

Having less of an appetite means you’re reducing how much you eat, including nutrients. And that causes your body to lose not just fat, but lean mass from muscles, bones, and organs. As an addition to a nutrient-dense diet, a multivitamin helps you get (at least) a baseline of what your body needs to keep that muscle. For women, go with a prenatal vitamin (unrelated to childbearing ability/interest; you’re in it for its extra calcium and iron); men can go with any daily multivitamin. The main thing to look for is at least 400 IU of vitamin D and 18 mg of iron. (Unfortunately, the calcium and vitamin D levels in a multi are usually still not enough to do the job solo, so you’ll likely still need a separate calcium and vitamin D supplement, says Cardel.)

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, ideally through fish, chicken, eggs, tofu, and legumes in your diet. But that can be difficult on such small portions, so you may want to supplement with protein powder.

The protein boost will 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.

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 on weight loss medications, you should be more in the range of 1.2-1.6 grams of protein per kilo, so that same 90kg person would need 108-144 grams of protein.

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, the next best thing is pea protein. WeightWatchers makes keeping track of macronutrients like protein simple. On the GLP-1 Companion 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.

Supplements for constipation

Psyllium fiber
Magnesium

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 is constipation, says Grunvald. If that’s happening for you, the first step is to make sure you’re drinking enough water (there’s a formula to figure out your personalized number, but you can also just check to make sure your pee is light yellow).

You also want to make sure you’re eating enough fiber; the U.S. Department of Agriculture recommends that adults consume between 22 grams and 34 grams of fiber per day, depending on age and sex. Generally, you want to get 14 grams of fiber for every 1,000 calories you eat. Yet more than 90 percent of women and 97 percent of men in the U.S. aren’t hitting those numbers. 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.

Still backed up? Consider psyllium husk. This is a natural fiber supplement that comes in powder form you dissolve in water (bonus: you also get those ounces in!) or take as a tablet. You can also add magnesium citrate (350 milligrams) powder dissolved in water before bedtime. It helps soften stool by drawing water into the small intestine, making it easier to go when you get up in the morning.

When to consider thiamine (vitamin B1)

Thiamine (Vitamin B1)

“A vitamin deficiency for people on GLP-1s that can be very dangerous is not having enough thiamine, also called vitamin B1,” says Grunvald, though it’s more common after bariatric surgery. Thiamine helps convert food into energy and keep your nervous system healthy. We get thiamine through a range of foods (black beans, fish, seafood, lentils, macadamia nuts, pork, sunflower seeds, whole wheat bread, and yogurt, among others), but diets lacking these, or people who already have certain conditions (including hyperthyroidism or liver disease) or take some kinds of medications (some diuretics, cardiovascular drugs, and antiseizure medications) are more likely to lack thiamine.

“While a thiamine deficiency isn’t common, if it goes undetected for a long time, it could cause very serious problems,” says Grunvald. “Yet if it’s caught early, it's easily treated with a B1 supplement.”

He says people who are more likely to be at risk for a B1 deficiency include African Americans, anyone taking water pills (diuretics), or anyone who uses alcohol heavily. Especially if you’re at higher risk, make sure your doctor does a blood test to check your B1 levels.

How can you determine the right supplements for you?

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 Cardel agree that your specific supplement routine should be personalized. Sadly, most people aren’t getting that guidance from an MD or RD, 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 Cardel.

Cardel recommends meeting with WeightWatchers 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.

The bottom line

There are lots of positive health benefits from using a GLP-1 to eat less and lose weight, but there are also a few significant risks, 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, magnesium, and vitamin D — but thankfully daily supplements are an easy way to fill in nutritional gaps. 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.