Eating & nutrition
Vitamins and supplements to discuss on a GLP-1
October 2, 2026 · 6 min read · Medically reviewed by Bryan Milton, MD · Reviewed October 2, 2026
Eating much less means taking in less of everything. Which gaps are worth asking about, why testing beats guessing, and what to tell your clinician.
This article deliberately recommends nothing. Eating substantially less does create real nutritional gaps, and the useful response is finding out which ones you actually have — because supplementing a deficiency you do not have is at best wasted money and at worst a problem of its own.
Why gaps appear
Micronutrient intake tracks food volume fairly closely. Halve what you eat and you broadly halve what you take in, unless the composition changes to compensate. On a GLP-1 the composition often moves the wrong way: less variety, fewer vegetables, less red meat, more of whatever is tolerable. Add vomiting or diarrhea and absorption suffers too.
What is worth asking about
| Nutrient | Why it comes up |
|---|---|
| Protein | The first thing a suppressed appetite drops; central to protecting lean mass |
| Iron | Low intake and reduced red meat; deficiency causes fatigue and hair shedding |
| Vitamin B12 | Lower intake of animal foods; also affected by some other medications |
| Vitamin D | Commonly low independent of diet; worth knowing your level |
| Calcium | Drops with dairy intake; relevant to bone health during weight loss |
| Folate | Tracks vegetable intake; particularly relevant if pregnancy is possible |
| Fiber | Not a micronutrient, but the most common real gap — see the fiber article |
Why testing beats guessing
Because the symptoms overlap. Fatigue could be low intake, iron deficiency, B12 deficiency, dehydration, poor sleep, thyroid disease, or the medication. Hair shedding could be rapid weight change or iron deficiency. Guessing means you may supplement the wrong thing for months while the actual cause goes unaddressed. A blood test answers in a week what a supplement cupboard never will.
Ask your clinician whether labs make sense in your case. Lab orders are included at no extra cost in GLP's programs when a clinician requests them.
Where supplements carry their own risks
- Iron should not be taken without evidence of deficiency; excess iron is harmful and it commonly causes constipation, which you may already be managing.
- Fat-soluble vitamins (A, D, E, K) accumulate, so high doses are not harmless.
- Several supplements affect the absorption of other medications depending on timing — calcium and iron are notable.
- Herbal products interact more than people expect and are not quality-controlled like medicines.
- Electrolyte powders are often high in sodium, which is not appropriate with high blood pressure, heart failure or kidney disease.
What to tell your clinician
Everything you take, including things you think of as food rather than medicine: multivitamins, protein powders, greens powders, electrolyte sachets, herbal teas taken for an effect, and anything a previous provider added. Also tell them if your compounded preparation contains anything beyond the active ingredient — B12 is sometimes included, and that is relevant to whether you need more of it.
The thing that is not a supplement question
If you are supplementing because you cannot eat, the supplements are not the answer. Being unable to eat is clinical information: tell your care team, because holding or adjusting the dose may be the right response.
This article is educational and is not a substitute for personalized medical advice. Whether any medication is appropriate for you is a decision for a licensed clinician who has reviewed your health history.