My doctor’s whole conversation about starting a GLP-1 lasted maybe six minutes. Injection sites, nausea, call if you throw up more than once. Nothing about the leg cramp that woke me up at 2am four months in, nothing about the extra hair collecting in the shower drain, nothing about why I was tired in a way three extra hours of sleep didn’t touch.
Turns out none of that is random. It’s math. When you go from eating 2,200 calories a day down to 1,400, you’re not just skipping dessert, you’re cutting protein, magnesium, potassium, fiber, all of it, by roughly the same third. The medication doesn’t know a donut from a piece of salmon. It just wants you eating less, and less of everything adds up fast if nobody tells you to course-correct.
So here’s what I’d stock in the cabinet if I were starting a GLP-1 today, knowing what I know now. Ten things, most of them under fifteen dollars, that patch the specific holes this class of medication tends to leave. Pin it now, because month three or four is usually when people start feeling this stuff, not month one.
Why a Medication for Appetite Turns Into a Nutrition Problem
Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) work by making you feel full sooner and staying full longer, which is the entire point and it works remarkably well, no matter which brand name is on the pen. The part that doesn’t get explained at the pharmacy counter is that when you eat 1,400 calories a day instead of 2,200, you’re not just cutting out the extra slice of pizza.
You’re cutting protein, fiber, magnesium, potassium, and vitamin D right along with it, because most people weren’t eating a nutrient-dense 2,200 calories to begin with.
A retrospective study of more than 461,000 adults on GLP-1 receptor agonists found that nearly 13 percent were diagnosed with a nutritional deficiency within six months, and that climbed to over 22 percent by the one-year mark, according to research published on PMC.
Vitamin D deficiency alone showed up in 7.5 percent of patients by six months and 13.6 percent by a year. Three percent were diagnosed with actual muscle loss within twelve months of starting.
A separate, smaller study that tracked what GLP-1 users were really eating found the gaps were even more specific than “not enough calories.” Ninety-eight point six percent of participants were under the recommended intake for potassium. Almost 90 percent were under on magnesium.
Fiber intake averaged 14.5 grams a day against a 28 gram recommendation, about half of what it should be, per the cross-sectional study in Frontiers in Nutrition. Those aren’t rare edge cases. That’s most people on the medication.
None of this means the medication is broken or that something’s wrong with you specifically. It means eating on purpose, at a much smaller volume, takes more deliberate choices than eating on autopilot ever did. Sometimes the easiest choice is a supplement instead of trying to chew your way to 28 grams of fiber on a stomach that wants a third of what it used to.
The GLP-1 Stack
Ten things, in the order I’d prioritize them if I were starting from zero. The first three matter for almost everyone on a GLP-1. The last few depend more on your specific situation, and I’ll tell you plainly where the evidence is solid and where it’s still catching up.
1. Protein Powder
This is the one nobody should skip. When researchers looked at what happens to muscle during weight loss without a dedicated effort to preserve it, they found that 20 to 25 percent of the weight men lost through calorie restriction was skeletal muscle, and 10 to 15 percent for women, cited in that same PMC review above.
Muscle isn’t just about how you look in a swimsuit, it’s your metabolism, your strength as you age, and the thing standing between you and a hip fracture at 70.
The fix is almost embarrassingly simple, eat enough protein, and a shrinking appetite makes that hard to do through food alone. Most people on a GLP-1 do better aiming for 25 to 35 grams of protein at each meal, three times a day, than trying to hit a big number all at once.
Stirring a scoop of a plain, no-sugar whey isolate into anything, yogurt, oats, a soup, a smoothie, closes the gap without adding volume you don’t have room for. I keep Isopure Unflavored Whey Protein Isolate around for exactly this, since it disappears into whatever you’re already eating instead of tasting like a shake you’re forcing down.
2. Creatine Monohydrate
Creatine has been the most studied supplement in sports nutrition for thirty years, and it’s finally getting looked at specifically in the context of GLP-1 medications.
A 2026 perspective piece proposed that incretin-based drugs like semaglutide and tirzepatide can pull as much as 40 percent of total weight lost from muscle tissue rather than fat, and argued that creatine, especially paired with resistance training, could help hang onto more of that muscle, according to the analysis published in Clinical Nutrition Open Science.
To be clear about what that means, the researchers are calling creatine a “promising strategy worth studying” in GLP-1 users specifically, not a proven fix, because that exact trial hasn’t been run yet. What thirty years of research outside the GLP-1 world does show, pretty convincingly, is that creatine helps hold onto lean mass during weight loss and boosts strength once you’re doing any kind of resistance work at all.
Five grams a day of plain Nutricost creatine monohydrate, no loading phase required, no fancy flavored version needed. If lifting weights isn’t part of your routine yet, this is a good excuse to start, even two sessions a week changes what your body does with the creatine.
3. A Soluble Fiber Supplement
If you’ve talked to anyone on a GLP-1 for more than five minutes, constipation has probably come up. It’s one of the most common complaints, and it’s largely a volume problem, you’re eating less food overall, which means less bulk moving through your system, on top of a medication that already slows digestion down.
A 2026 review in PMC on dietary fiber and GLP-1 receptor agonists lays out how fiber intake and these medications interact, and why getting enough of it matters more, not less, once you’re on one, per the full review here.
That Frontiers study mentioned earlier found the average GLP-1 user was eating about half the recommended 28 grams of daily fiber.
Mixing a scoop of NOW Psyllium Husk Powder into water, or into that same protein shake, is the fastest way to close that gap without needing to eat a bigger plate of vegetables than your stomach currently wants. Start with half a scoop, fiber added too quickly on top of an already slower gut can backfire into bloating before it helps.
4. Electrolytes
That same nutrient intake study found 98.6 percent of GLP-1 users fell short on potassium, and dehydration was formally diagnosed in nearly 3.5 percent of patients by the one-year mark in the larger PMC cohort.
Both numbers point at the same problem, eating and drinking less overall means less sodium, potassium, and magnesium coming in through food and fluids, and that combination is exactly what leaves people lightheaded, crampy, or randomly exhausted for no obvious reason.
One LMNT sugar-free electrolyte packet, mixed into water once a day, covers the gap without the calories or additives in sports drinks built for a different purpose entirely. Look for one with real potassium and sodium listed, not just a splash of added vitamin C and a marketing label. This matters even more on the days you’re nauseous and drinking less water than usual, which is exactly when your body needs it most and wants it least.
5. Vitamin B12
B vitamin deficiencies showed up in 1.3 percent of patients by six months and doubled to 2.6 percent by twelve months in that large cohort study, and B12 in particular is worth paying attention to since it’s absorbed through a part of digestion that a slower gut can interfere with over time.
Low B12 shows up as fatigue that doesn’t match how much you’re sleeping, brain fog, and for some people, the hair shedding that tends to get blamed entirely on rapid weight loss when a nutrient gap is quietly making it worse.
Look for a sublingual or methylated B12 supplement, the kind that dissolves under your tongue rather than needing to be broken down by a stomach that’s already working slower than usual, is the more reliable route here. It’s inexpensive and low risk, which makes it an easy one to just add rather than debate.
6. Vitamin D
This is the deficiency the data agrees on most consistently. The large cohort study found vitamin D deficiency diagnosed in 13.6 percent of patients by one year, and the smaller nutrient tracking study found a startling number, only 1.4 percent of GLP-1 users were meeting the recommended intake for vitamin D through food and typical supplementation. That’s not most people falling a little short, that’s nearly everyone falling well short.
Vitamin D isn’t just a bone health nutrient, it plays a role in mood, immune function, and how your muscles contract, which matters double when you’re also trying to hold onto muscle mass through the rest of this list. A daily Nature Made D3 supplement, 2,000 to 4,000 IU for most adults, is cheap enough that there’s not much reason to skip it, though if you want an exact number for your situation, a simple blood test settles it.
7. Magnesium
Almost 90 percent of GLP-1 users in that nutrient tracking study were under the recommended intake for magnesium, and it’s one of the more noticeable gaps to feel in real life. Magnesium plays a role in muscle relaxation, sleep quality, and mood regulation, and low levels tend to show up as the specific 2am calf cramp that jolts you awake, along with a wired-but-tired feeling that no amount of coffee fixes.
Double Wood magnesium glycinate is the form worth looking for specifically, it’s gentler on a stomach that’s already dealing with enough, unlike magnesium oxide, which is cheaper but tends to just speed up a trip to the bathroom instead of getting absorbed. Taken in the evening, it doubles as one of the more underrated sleep aids that isn’t marketed as one at all.
8. Omega-3 Fish Oil
This one doesn’t show up in the deficiency studies the same way potassium or vitamin D do, but a 2025 narrative review on supplement use during GLP-1 treatment flagged it as one of the stronger recommendations in the whole paper, rating the evidence behind it as strong.
The review, published in Obesity Pillars, points to fish oil’s role in supporting muscle quality and fighting the kind of low-grade inflammation that tends to climb during fast weight loss.
The review’s recommended dose is at least 1 gram a day of combined EPA and DHA, the two active omega-3s, not just “fish oil” in general, since a lot of cheap bottles on the shelf barely clear a few hundred milligrams of the parts that matter most. A decent Carlson’s Finest Fish Oil with that dose on the label, taken with a meal so it doesn’t repeat on you, covers it.
9. A Probiotic
Fiber handles the volume side of GLP-1 constipation. A probiotic handles the other half of that equation, the bacteria doing the digesting in the first place. That same narrative review recommends a dose somewhere between 1 and 30 billion CFUs, with Lactobacillus or Bifidobacterium strains specifically, and rates the evidence behind it as moderate, promising but not yet proven in GLP-1 users directly.
Outside the GLP-1-specific research, probiotics have a decent track record for improving stool consistency and gut diversity in general, and some data even points to a modest effect on weight and body fat independent of diet. Look for a Physician’s Choice probiotic in that CFU range rather than the cheapest bottle on the shelf, potency drops fast on probiotics that weren’t stored or dosed properly.
10. NAD Support (NMN)
This one’s different from the other nine, and I’d rather undersell it than oversell it. NAD levels drop with age no matter what medication you’re on or off, and NMN is the supplement most people reach for to try to prop that system back up.
The human trials on NMN are a mixed bag so far, some show real movement in markers of cellular energy, others barely move the needle, and none of them have looked specifically at GLP-1 users. Think of it less as a fix for anything above and more as a bonus round, worth adding once the first seven items are covered and there’s still room in the budget.
Where it might help most is the fatigue piece. A body running on fewer calories and rebuilding tissue while losing weight is already asking a lot of its energy systems, and cellular energy production is exactly what NAD is involved in.
I’ve used Renue by Science’s Pure Powder NMN for this, it’s third-party tested and one of the more established names in this specific niche rather than a random bottle that showed up on Amazon last month. Code FLOW10 knocks 10 percent off if you decide to try it.
The Stack at a Glance
Mistakes People Make With This Stack
- Starting all ten at once. Adding fiber, magnesium, and a new protein powder in the same week makes it impossible to tell what’s helping and what’s upsetting your stomach. Add one thing every few days instead.
- Treating protein powder as a meal replacement. A shake with no actual food alongside it doesn’t carry the same fullness or nutrients as an actual meal. It’s a gap filler, not a dinner substitute.
- Skipping the blood test. If you can get one, a basic panel checking vitamin D, B12, and electrolytes before you start guessing tells you which of these matter for your body instead of supplementing blind.
- Buying the cheapest magnesium on the shelf. Magnesium oxide is common because it’s inexpensive, not because it works well. It mostly just adds a trip to the bathroom instead of getting absorbed where you need it.
- Assuming supplements replace the conversation with your prescriber. If fatigue, cramping, or hair loss is severe, that’s worth mentioning at your next appointment rather than quietly supplementing around it for months.
FAQ
Do I really need all ten of these?
No. Protein, fiber, and electrolytes cover the majority of what most people are missing and are the ones worth starting with. The rest depends on your bloodwork, your appetite level, and your budget. This is a menu, not a mandate.
Can these supplements interact with semaglutide or tirzepatide?
Everything on this list is generally considered low risk alongside GLP-1 medications, but “generally low risk” isn’t the same as cleared for your specific situation. Mention what you’re taking at your next appointment, especially if you’re also on other medications.
Is muscle loss on a GLP-1 really that common?
More common than most people expect, and it’s largely preventable with enough protein and some resistance training, not something that happens to everyone regardless of what they do. It’s a reason to be proactive, not a reason to panic.
What should I take first if I can only afford one or two things right now?
Protein powder and a basic vitamin D3, in that order. They’re the cheapest items on this list, they address the two most universally documented gaps, and neither requires any guesswork about your individual situation to start safely.
Where can I buy a good NMN supplement?
I use and recommend Renue by Science’s Pure Powder NMN, it’s third-party tested and one of the more established options in a supplement category that has a lot of questionable ones. Code FLOW10 gets you 10 percent off.
Start With One, Not Ten
If this list feels like a lot, that’s because it covers a lot of ground at once. You don’t need to walk out and buy all ten today. Pick the one or two that match what you’re feeling right now, tired, crampy, backed up, whatever it is, and start there. The rest can wait until you’ve built the habit of taking anything consistently in the first place.
Your GLP-1 is doing its job. This stack is just making sure the rest of your body can keep up with it.
All information here is for educational purposes only and is not medical advice. Talk to your prescriber before starting any new supplement, especially alongside a GLP-1 medication.
This article contains affiliate links. BrainFlow may earn a commission on qualifying purchases at no additional cost to the reader. We only recommend sources we trust.
