Fatigue On GLP-1s: Why It's Happening And How To Fix It

We break down why fatigue can show up on GLP-1 medications and why the fix depends on the real cause, not a one-size-fits-all trick. We walk through four common drivers and the practical next steps that help you feel energized while still moving toward your weight loss and metabolic health goals. 
• underfueling on GLP-1 due to strong appetite suppression and overly aggressive calorie restriction 
• balancing calories with a slight deficit to support weight loss without draining daily energy 
• macronutrient balance and why extreme low-carb approaches can leave some people exhausted 
• when to consider discussing a lower GLP-1 dose with your doctor 
• micronutrient basics and who needs extra attention due to absorption issues 
• three key labs to ask about for fatigue: vitamin D, ferritin, and vitamin B12 
• vitamin D targets, sunlight timing, food sources, and safe supplementation monitoring 
• iron deficiency fatigue despite a normal CBC and why ferritin matters 
• iron treatment options including food, every-other-day oral iron, and IV iron when needed 
• sleep quantity and sleep quality as major fatigue drivers 
• sleep hygiene fundamentals and CBT-I as first-line care for primary insomnia 
• obstructive sleep apnea symptoms, home testing, and CPAP as the most effective treatment 
• normal temporary fatigue during weight loss and when it signals a bigger problem 
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Transcript

Welcome And Medical Disclaimer

Dr. Lindsay Ogle, MD 0:00

Welcome to the Modern Metabolic Health Podcast with your host, Dr. Lindsay Olge, Board Certified Family Medicine and Obesity Medicine Physician. Here we learn how we can treat and prevent modern metabolic conditions such as diabetes, PCOS, fatty liver disease, metabolic syndrome, sleep apnea, and more. We focus on optimizing lifestyle while utilizing safe and effective medical treatments. Please remember that while I am a physician, I am not your physician. Everything discussed here is provided as general medical knowledge and not direct medical advice. Please talk to your doctor about what is best for you.

Why GLP-1 Can Make You Tired

Dr. Lindsay Ogle, MD 0:43

If you are on a GLP1 medication and you are tired, you're going to want to listen to this talk. Many of my patients are on GLP1 agonist, and many of them do experience fatigue as a side effect or related symptom while on their GLP1 treatment. We're going to talk about four reasons why that might be. And the first thing I want to say is that you want to identify why you're feeling tired. Many people are looking for the one treatment that's going to help, you know, them because it helps somebody else. But the truth is that we need to know why you're having this symptom so we can treat that underlying reason. And so today we're going to talk about four common reasons why you're tired on your GLP1 medication so you can identify it and then treat it and feel energized and feel better.

Underfueling And Appetite Suppression

Dr. Lindsay Ogle, MD 1:43

So the first one that we're going to talk about today is underfueling. If you are not eating enough food, not enough calories, you are going to feel very tired. The reason that we well, there are many reasons why we eat and that we need calories, but one of them is that calories give us energy. And so if you are underfueling and you are severely calorie restricted, then your energy, the calories that you intake, they are going to be regulated to maintain your bodily functions that are vital for living. So your heart has to beat, your lungs have to breathe, your brain has to function, your kidneys have to filter out all the toxins, your liver has to filter out all of the toxins, you have to create hormones, you have to regulate your body temperature. There are so many things happening in your body at all times that take energy to accomplish. And so if you are not getting a lot of calories in the day, then your calories are going to be completely spent on these bodily functions, required to just survive. And you're not going to have extra energy to go towards movement and more towards your brain for um cognitive function because you are running on empty. This is so, so, so important because diet culture, diet mentality tells us that we need to restrict, restrict, restrict, restrict calories, restrict certain macronutrients. And if you are one of the people who have significant appetite suppression on GLP1 medications, then it is hard to get adequate calories in. But we have to fight against diet culture and we have to address that appetite suppression on GLP1 medications to ensure you're getting enough calories. And what is enough calories? There are really scientific ways that you can figure this out. So there are places where you can go where you can get specific testing done to see how many calories your body needs at rest. There are online calculators that can make estimates. There are rough recommendations that you can again find charts online based on your age and height and sex and weight activity level that can make those estimates. And that can be a good starting place, but none of them are truly accurate. And the best thing to do truly is to log and count yourself and make adjustments based on how you're feeling. And this is one of the times that I highly, highly, highly recommend that you work with a board-certified obesity medicine physician, and most likely even a better person would be a registered dietitian. They are going to be able to review your food log with you and make recommendations for adjustments and to make sure that you are, again, getting a good amount of calories in to support your bodily functions as well as provide energy for you to live the life that you want to live and do everything that you want to do in a day. And then keep it at a slight calorie deficit so you can achieve your weight loss goals. So this is a balance that we want to achieve and is best done alongside a qualified physician and registered dietitian. I will also say that if you are overly appetite suppressed on your GLP1 medication, it may be time to talk to your doctor about reducing your dose because that is not the goal of these medications. It's not to take your appetite away, it is to regulate your appetite to an appropriate and healthy level so that you can eat healthy foods, achieve enough calories and nutrients in the day, but not to overdo it and to just make that a little bit more balanced for you throughout the day. In addition to calories, I also think about macronutrients. And there are so many conflicting diets out there, recommendations from physicians, dieticians, influencers about what the best diet should be. And right now, low-carb diets are very, very popular, even you know, more extreme versions like ketogenic diets or carnivore diets that tell you to significantly reduce or completely eliminate carbohydrates. But the truth is that that's not required for optimal health, and that many people are going to feel very tired on these diets because our body's preferred energy source is carbohydrates. That does not mean that you need sugar to function and have energy, but it does mean that having complex carbohydrates, fruits, vegetables, whole grains, um, that is going to help support your body to function well and have lasting and sustainable energy throughout the day. So having a balanced diet with you know a good amount of protein, healthy fats, and complex carbohydrates, specifically, you know, foods that contain fiber, is going to be important to you know regulate your energy levels. And definitely working with a dietitian is going to help you figure this out because it is a lot to navigate, especially when you're taking advice from multiple people online. Having somebody who is trained in this field of obesity and nutrition, who is going to focus on you and your goals and your preferences is going to give you the most optimal results.

Micronutrients And Key Labs

Dr. Lindsay Ogle, MD 7:52

The next thing I want to think about is micronutrients. So here we're talking about vitamins and minerals. And if you are having a well-rounded whole food-based diet that has, you know, adequate intake, like we talked about in the point before, then you are probably reaching your micronutrient goals, especially if you do not have any other health conditions that would impact your nutrient absorption. So conditions I would think that would decrease absorption of micronutrients would be celiac disease, inflammatory bowel disease, history of GI surgeries, metabolic and bariatric surgery. There are several conditions that may alter the absorption of micronutrients, and for those people, you would need a higher focus and emphasis on this micronutrient category and working with your specialist and a dietitian can be very beneficial here and periodically checking labs. A lot of people will look to have a very extensive panel done here. And there are times where that might be appropriate, but I want to highlight three labs that I would recommend for all of my patients who are feeling tired on a day-to-day basis. Truly, whether or not they're on a GLP1 medication, but definitely if they are. Those three labs are vitamin D, iron levels, and B12. These are the most common deficiencies that we see when patients who are experiencing fatigue. So vitamin D levels, we want to get those checked. We want a number of 30 or greater. If you have low vitamin D levels, there are lots of dietary sources of vitamin D that sometimes people forget. So you can Google vitamin D dietary sources and find some foods that you enjoy and introduce those into your diet. You also can get vitamin D from the sun. We do not want more than about 20 minutes of sun exposure without sunscreen. But getting 20 minutes during the day can help boost your vitamin D levels. This can be extremely beneficial for people like myself who work indoors. Getting in about that 20 minutes can help with those vitamin D levels. And also, if you get it done in the morning, it can help with your sleep later on at night. And we're going to talk about sleep later in this talk. And then last, you can have supplements. And so for patients who are severely low on vitamin D, so typically 10 to 15, they're level 10 to 15 or lower. I start them on prescription strength vitamin D supplementation, which is 50,000 international units each week for at least eight weeks, and then we can typically switch to an over-the-counter vitamin D supplement. I usually recommend around 2,000 IU daily, and we do want to check those levels at least a couple of months after supplementation to make sure that they have gone up into a normal range. We also don't we want to make sure they're going up into the normal range, but we also want to make sure that we're not oversupplementing because very high levels of vitamin D can be dangerous and can cause significant issues. And so we want that sweet spot in a healthy range. Next is iron levels. And I don't see this checked that often in the recommended way. So oftentimes patients get a complete blood cell count, which will look at their red blood cells, white blood cells, and platelets. And if that is normal, then they often don't get their iron levels checked. And the thought process here is that if your iron is low for long periods of time, then it is going to negatively impact your hemoglobin, which is a protein in your red blood cells that carries oxygen throughout your body. So that's why you can feel very tired because your body's not getting the oxygen that it needs because the hemoglobin is low. But um, you can have very low iron levels and still have a normal blood cell count and still have fatigue. And this can be because the hemoglobin is still not optimal, but it hasn't been or gotten to the point where it is reflected in the complete blood cell count, but the iron levels are still very low, and so what I recommend is a ferritin level. Ferritin is a kind of an estimate of iron stores, and I see this low all of the time for patients who have had a normal blood cell count and sometimes even normal iron panels because not all iron panels will check for ferritin.

Speaker 13:14

And this these labs are outside the scope of this talk.

Dr. Lindsay Ogle, MD 13:23

Lab that just shows iron, um, the amount of iron in your blood is very sensitive to what you ate that day. So if you ate something that had iron in it, or you had an oral iron supplement, or there was iron in your multivitamin, then it's going to show that the level is normal. But that does not mean that you have normal iron stores in your body. And the ferritin is what is going to tell us that. It's also important to know that ferritin can be falsely elevated. It can be elevated if you're having a lot of inflammation in your body. So it's not a perfect test, but it's a really, really good screening test, and your doctor can then follow up with additional testing if needed. But if your eye if your ferritin is less than 50, 5, 0, and you are feeling tired, then that suggests that you should have iron supplementation. And this is very, very different than what you're going to see on your lab results because a ferritin of 40 is going to classify as normal, and every lab is a little bit different, but their cutoff is much lower than what we should be going after. And so if you are symptomatic and you're and your ferritin is below 50, then you should be treated as having iron deficiency causing fatigue. If your ferritin is showing up as low, then your stores are very low and they they should be treated appropriately. Same thing here, you can Google iron-rich foods and you can increase those amounts of foods that you enjoy. You can try over-the-counter iron supplements, and it is actually recommended to take every other day, which can help increase tolerance and increase or maintain absorption. The most common side effects can be stomach upset, stomach pain, nausea, constipation, or even diarrhea for some people. They can be truly poorly tolerated, but it is worth trying if you have low iron levels. You can take it with food. So have it with some food. But you want to avoid calcium-containing foods when you take this because that will prevent the iron absorption. Many people, like I said, don't tolerate oral iron and they need IV iron infusions, and this is something that can be really beneficial very quickly. So if you are struggling to maintain your iron levels on, you know, through diets and through oral supplementation alone, ask your doctor about IV iron because that may be available to you and may help you feel better very quickly. This is also what's recommended for patients who have had um bariatric and metabolic surgery or metabolic and bariatric surgery because um it iron can be difficult to absorb after surgeries, and so the iV iron is often the you know most efficient route to get your iron supplies up. Again, outside of the talk, outside of the scope of this talk, but if you have low iron levels, it's really important to ask your doctor why. There are many, many, many reasons why you may have low iron. For women, most common is through menstrual blood loss with our monthly periods. Um, but if you're having really heavy periods, it's important to look into why that is happening. Um, but if you're over 45 and you have low iron, then it's really, really important to get colon cancer screening because colon cancer may lead to iron deficiency. Um very important to ask why do I have low iron levels? And then the third micronutrient that I think about with fatigue is vitamin B12. Vitamin B12, we get this through animal products, so through meat and dairy products, you can get your B12 stores. And if as long as you have good absorption, a healthy GI tract, then you will absorb it and it is stored for years at a time. So this is not as common as vitamin D and iron deficiency, but we do see it. Um, there can be again several reasons why. Um, and this is also one where the lab can show a normal value, but if you're in the low normal range of B12, then it's you still might benefit from supplementation. Supplementation can be oral over-the-counter on B12 supplements as long as you have that healthy gut that will absorb the oral supplement. If you have a GI abnormality and that is why you're not absorbing it, or if you have severe symptoms or very, very low levels, then it might be beneficial to have the intramuscular and injectable version of B12.

Sleep Problems That Drain Energy

Dr. Lindsay Ogle, MD 18:46

Um, all right, the third reason that you may be tired on your GLP1 medication is poor sleep, and this could be poor sleep quantity or quality. Sleep is something that gets overlooked a lot because it can be unfortunately difficult to manage, but there are a couple of things that I really want to highlight here. I did do a talk a few years ago now about sleep, so I'll link that here. Conditions to consider are primary insomnia, which can respond very well to sleep hygiene. We also want to screen for and think about obstructive sleep apnea, which is very common in people who are living with obesity. And then last, we want to think about secondary insomnia related to other mental health conditions like anxiety or PTSD. So, first with primary insomnia. So this is chronic insomnia struggling to fall asleep and stay asleep. And there are sleep hygiene protocols to follow that again I talked about in more detail, but in my prior video, but I will highlight a few here. So we want to try our best to have a regular sleep wake cycle. So we want to go to bed at the same time and wake up at the same time, even on the weekends. This helps train our brain and our body that we when we when it is let's say 10 o'clock, it is time to for sleep, and when it's 6 a.m. it's time to wake up. Um so that is extremely, extremely helpful whenever possible. We want to get that sun exposure in the morning, like we mentioned earlier, and then in the evening time we want to avoid light exposure as much as possible. Blackout curtains in the room, sleeping with an eye mask can be extremely beneficial. Want to keep the room a little bit cooler around 68 or 67, 68 degrees if possible. We want to keep the room for sleep and sex only. So you do not want to be watching TV in your room, you do not want to be doing work in your room, you do not want to be eating in your bed. You want to again train your brain and your body to know that when you are in your bedroom and you're getting ready for bed, it is ready for sleep. We're not doing other activities at that time. We want to avoid uh stimulants, so caffeine or other stimulants later in the day, and also avoid alcohol, which can disrupt sleep. If you are struggling to fall asleep, then you actually, after 20 minutes, you want to get out of bed and do another activity. So something that's relaxing to you, maybe stretching a little bit. You can read a book in a different room until you're tired and then you want to try again. There's also some strategies called sleep restriction. This is done through CBTI, Cognitive Behavioral Therapy for Insomnia. You can see it. A CBTI specialist for this. There's also some free apps which I will link below and that can be extremely helpful in reviewing the sleep hygiene as well as the sleep restriction to help treat primary insomnia. And this is the number one recommended treatment for primary insomnia. There is no medication that is recommended because while they may cause you to feel very tired and it appears that you sleep more, your sleep quality goes down on sleeps on sleep aids. So CBTI is the recommendation for primary insomnia and is very effective. So sleep apnea, very common in people who are living with obesity. More common as we get older with family history, with increased neck circumference for men, and with a family history. Symptoms would be not feeling rested after a full night's sleep, having somebody tell you that you're snoring really loud or that you stop breathing when you sleep, waking up with headaches in the morning, and waking up feeling short of breath or gasping for air. If you are experiencing those or you have any of the other risk factors, definitely talk to your doctor about the possibility of obstructive sleep apnea. And the testing now for the vast majority of people can be done at home, just with a one-night overnight sleep study in your home, and very, very convenient, quick, and fairly accurate. Some people need to follow up with an in-person sleep study, but that's fairly rare. And treatment, we have lots of different treatments now. CPAP machine remains the main recommendation, most effective and immediately effective. And then Zbound is FDA approved for moderate to severe obstructive sleep apnea in addition to CPAP. So that medication may be helpful with your symptoms as well. And then last, um, secondary insomnia to other psychological conditions like anxiety and PTSD. This can be difficult to talk about, but is important to bring up if you are concerned, because again, there are treatments available. Cognitive behavioral therapy or other types of therapy can be very beneficial. As well as medication. This is one of the ones that medication can be, you know, probably the most beneficial for. For PTSD, if you're having nightmares that are preventing you from wanting to go to sleep, so you're avoiding sleep because of your PTSD-related nightmares, then there's a medication called Prasosin that many people do very, very well with. And I've started this with patients and their sleep improved pretty dramatically very quickly. Anxiety, same thing. There are lots of different medications that can help with anxiety and or therapy can be very beneficial, and then you'll see improvements in your sleep as the control of anxiety or another psychological condition improves.

Normal Weight Loss Fatigue And Next Steps

Dr. Lindsay Ogle, MD 25:11

And then finally, it can be expected to be a little bit tired as you're losing weight. So this is a known physiologic effect of weight loss. Weight loss is not passive, it's active. Your body is burning energy and it is working on losing the weight for you. And so, because it's burning more energy, it can lead to temporary fatigue, and that's expected. But it should not be so severe that it's negatively impacting your quality of life. And so, if it's negatively impacting your quality of life, consider one of the other topics that we mentioned: underfueling micronutrient deficiencies or poor sleep, quantity or quality, and talk to your doctor about those and come up with an approach to improve or to formally diagnose and then to improve that underlying cause, so then you can have more energy and enjoy your life more because that is the ultimate goal. That is what you know myself as an obesity medicine physician is hoping for all of my patients, and I'm sure that is what you are looking for as well when you are treating your obesity. So I really hope this was helpful. Do you have any other side effects on your GLP1 that you would like me to specifically address? I would love to hear it and answer your questions. If you're on YouTube, you can just comment them below. If you're on the podcast, you can send me an email at support at Missouri Metabolic Health.com or send me a message on Instagram or TikTok. I'd love to hear from you. Thank you for listening and learning how you can improve your metabolic health in this modern world. If you found this information helpful, please share with a friend, family member, or colleague. We need to do all we can to combat the dangerous misinformation that is out there. Please subscribe and write a review. This will help others find the podcast so they may also improve their metabolic health. I look forward to our conversation next week.