Ten GLP-1 Questions, Answered by the Evidence
GLP-1 medications now come with a long list of claims. Some are backed by large, careful trials, and some by little more than social media amplification. Here are ten questions I hear constantly, with a look at how well the evidence supports each answer.
1. Will it make me go blind?
Almost certainly not. The recent headlines about semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) and “blindness” refer to a specific condition called NAION, and the risk of it depends a great deal on the shape of your optic nerve.
NAION stands for non-arteritic anterior ischemic optic neuropathy. In plain terms, it is a small stroke of the optic nerve, right where the nerve enters the back of the eye. It typically causes sudden, painless loss of vision in one eye, often noticed on waking. Some vision usually remains, but the loss is often permanent, and there is no proven treatment.
In 2024, a group at Massachusetts Eye and Ear reported that their patients on semaglutide were several times more likely to develop NAION than similar patients on other drugs. That was a striking number, but those were patients already referred to a specialty eye clinic, which tends to exaggerate this kind of finding.
Larger studies of the general population have since been more reassuring. Some found roughly a doubling of risk; others found no increase at all. Even taking the less favorable figure, a doubling of a very rare event is still a very rare event: on the order of one or two extra cases for every 10,000 people treated for a year.
NAION does not strike optic nerves at random. The great majority of cases occur in people born with a small, tightly packed optic nerve head, which eye doctors call a “crowded disc” or a “disc at risk.”
Anything that briefly lowers blood flow to the nerve can cause swelling in a crowded disc: a drop in blood pressure overnight, untreated sleep apnea, erectile dysfunction drugs, dehydration. It is plausible that these weight-loss medications, which can lower blood pressure, cause fluid loss through nausea and vomiting, and drop blood sugar quickly, act as one more such trigger.
The patients I am most careful with are those who have already had NAION in one eye. Their other eye almost always has the same crowded anatomy and, even without any medication, carries about a 15 percent chance of the same event over five years.
Patients with crowded discs can still be treated with GLP-1s, but they should consider the following:
Getting tested, and if needed treated, for sleep apnea
Moving blood pressure medications to the morning
Cutting back on erectile dysfunction medications
Raising doses slowly and staying VERY well hydrated
NAION in a normally shaped optic nerve is unusual to begin with, so if your discs are normal, your risk on these medications should be very low indeed. In fact, when an apparent NAION occurs in someone with a normal disc, there is usually something else going on, such as giant cell arteritis, an inflammation of the arteries in older adults that needs urgent treatment.
2. What is retatrutide?
Retatrutide is an experimental once-weekly injection that is not yet FDA-approved. It acts on three hormone receptors (GIP, GLP-1, and glucagon), and the glucagon piece adds extra calorie and fat burning on top of appetite suppression. In plain terms, it leads to more weight loss. So why isn’t every doctor prescribing it?
What is sold online is a white powder in a vial, usually made overseas and labelled “for research use only, not for human consumption.” That label is there for one purpose only: to protect the company from lawsuits.
There is no guarantee of any of the following:
That it is retatrutide. No regulator has inspected the factory or tested the vial. It may be a different peptide, or a partly broken-down one.
That the dose is right. Vials can contain more or less than the label says, and the purity and strength of these products are known to vary widely.
That it is sterile. You are mixing a powder with water at your kitchen counter and injecting it. Contamination with bacteria, or with bacterial toxins that survive even when the bacteria do not, is a real risk.
That you measured it correctly. Converting milligrams into units on an insulin syringe is easy to get wrong, and a misplaced decimal point means a tenfold overdose.
There is a subtler concern as well. Poorly made peptides contain fragments and clumps that the immune system may treat as foreign. In theory, that could lead your body to make antibodies against the drug, which might matter if you later want to take the real thing once it is approved.
Retatrutide also has some side effects the approved drugs do not. The glucagon piece raises heart rate, and earlier trials reported heart rhythm disturbances and unusual skin sensitivity in some participants. We don’t yet have the results of large, long trials.
3. Do the pills work as well as the shots?
At the right dose, yes. Several pills are now FDA-approved: Rybelsus (oral semaglutide for type 2 diabetes), oral Wegovy (semaglutide 25 mg for chronic weight management), Ozempic oral tablets, and Foundayo.
In the OASIS 1 trial, oral semaglutide 50 mg daily produced weight loss comparable to the 2.4 mg weekly injection. More than two-thirds of participants lost at least 10% of their body weight and about one-third lost at least 20%, with the same familiar side effects.
The catch is convenience. Oral semaglutide has to be taken on an empty stomach with only a sip of water, because of the ingredient (called SNAC) that helps it get absorbed. Orforglipron (Foundayo), a different kind of GLP-1 pill with no food or water restrictions, has shown strong effects on blood sugar and HDL (“good”) cholesterol in comparison studies.
4. Will it help me live longer?
Possibly. The drop in death rates is consistent from study to study, but no trial has been designed to test longevity itself. A pooled analysis of 11 trials (about 90,000 patients) found significantly fewer deaths overall, including fewer from heart disease and fewer from other causes. In people with obesity but no diabetes, the SELECT trial showed a 19% reduction in deaths from any cause.
These benefits appear larger than the changes in blood sugar and weight alone would predict. That has caught the attention of aging researchers, who point to laboratory studies suggesting these drugs may slow the aging of cells and reduce oxidative stress. A 2025 report described a slowing of DNA-based “biological age” clocks over 32 weeks of semaglutide.
All of that is still early and needs confirming.
5. Can creatine protect my muscle while I’m on a GLP-1?
Patients on semaglutide (Wegovy) or tirzepatide (Zepbound) ask me this almost weekly. The short answer: creatine can probably help a little, but only if you are also lifting weights and eating enough protein, and nobody has yet proven it in people taking these medications. Here is how I think about it.
Whenever you lose weight, by any method, you lose some lean tissue along with the fat. In the major trials of these medications, roughly a quarter to 40 percent of the weight lost was “lean mass.”
That number sounds worse than it is. Lean mass on a body scan is not just muscle; it includes water, organs, and other tissue, and a smaller body needs less muscle to carry it around. Still, the concern is real, especially if you are over 60, were not very muscular to begin with, or are losing weight quickly. Muscle is what keeps you strong, steady on your feet, and independent.
What the evidence shows
With resistance training, it helps. In older adults who lift weights, adding creatine produces modestly more muscle and strength than training alone.
Without training, it does very little. Creatine works by letting you train a bit harder. It does not build or protect muscle while you sit idle.
In people on GLP-1 medications, it has not been tested. As far as I can find, no randomized trial has looked at creatine in patients taking these drugs. Studies of exercise and protein in this setting are under way; creatine is, so far, an educated guess based on other groups of people.
6. Can I stack it with other research peptides?
There is no good evidence for casually adding “research peptides” such as BPC-157, growth-hormone boosters, or melanocortin (tanning) peptides to a GLP-1. Nobody has studied whether those combinations are safe. For that matter, no one has studied most of these peptides in a serious way. Peptides sold online have tested at purities anywhere from 5% to 75%, with contamination by heavy metals including arsenic and lead. Safety aside, it is unclear whether any of the claims made for them can live up to the hype.
7. Will my hair fall out?
Hair loss is a surprisingly common side effect of rapid and significant weight loss. In part, this is due to stress on the body.
Under normal circumstances, most hair follicles are actively growing (a phase called anagen). A small percentage are resting (telogen) before they shed. When the body is under significant stress, such as severe illness, emotional crisis, starvation, or weight loss, hair follicles shift from growing to resting. The result is noticeable shedding, usually 2 to 4 months after the triggering event. Doctors call this telogen effluvium.
At the “root” of this unwelcome process is energy conservation. Hair follicles are among the most metabolically active structures in the body, constantly dividing and rebuilding. If calories are suddenly and sharply restricted, the body “triages,” putting survival ahead of appearance. The organs essential for life get the limited fuel, and hair growth, deprived of energy, cannot be sustained.
Nutrition is the key. Studies in patients having weight-loss (bariatric) surgery have linked hair loss afterward to low levels of zinc, iron, folic acid, blood proteins, and calcium.
The good news is that the hair loss that comes with weight loss is usually temporary. Once nutrition improves, hair follicles gradually return to their growth phase. For most patients, much of the shedding that began within a few months of weight loss resolves over the next 6 to 9 months. When there is no nutritional deficiency, there is no established treatment, because the problem typically corrects itself. In training, my mentor used to say, “Give your patient with telogen effluvium a hug.” Reassurance and education really are the main treatment.
That said, many people understandably want to do something while they wait. Topical minoxidil 5% is the most studied option for this kind of shedding, although it is an off-label use. It appears to speed regrowth rather than prevent shedding. In a small open-label study, patients using minoxidil showed meaningful increases in hair counts within weeks, and nearly 70 percent improved on standardized measures of shedding. Side effects were minimal, which makes it a reasonable choice for those who want to take action. Be aware, though, that the gains depend on continued use, and shedding may return if you stop too soon.
8. Does microdosing work?
Technically, nobody knows yet. In practice, most doctors feel it works well and are comfortable prescribing it. So what does it mean? Microdosing usually means taking 25–50% of the recommended starting dose, or stretching out the time between doses. It is an off-label approach driven by side effects, cost, and shortages, and solid evidence is essentially absent.
Dosing every two weeks may preserve roughly 70–75% of the weight loss, and less frequent dosing after a plateau may hold onto results at lower cost.
The safety concerns are practical ones: compounded products, improvised measuring such as “click counting,” and dosing errors.
9. What about surgery for loose skin afterward?
It is a reasonable option, and early results are encouraging. People who have lost a great deal of weight on GLP-1s are a new and growing group of body-contouring patients. They differ from patients who have had weight-loss surgery: they have no prior surgical scars and often have better nutrition.
In comparison studies, GLP-1 patients more often sought breast procedures and had less bleeding during surgery, with similar rates of infection, wound separation, and blood clots. A series of tummy-tuck (abdominoplasty) cases found better blood protein levels and a trend toward fewer complications than in patients who had lost weight through bariatric surgery.
Three issues matter around the time of surgery. These drugs slow the emptying of the stomach, so food can still be there despite standard fasting, which raises the risk of it getting into the lungs under anesthesia. Loss of muscle can affect tissue quality. And wound healing needs adequate protein, 60–120 g a day around surgery. Standard guidelines on timing do not yet exist.
10. Can it help me get pregnant?
It may, mostly indirectly, and it must be stopped before conception. GLP-1 medications improve fertility largely through weight loss and better insulin sensitivity, with possible direct effects on the hormone signals between the brain and the ovaries.
In women with obesity and PCOS, pooled studies (chiefly of liraglutide) show more regular cycles, lower weight and insulin resistance, and lower male-hormone levels, often beating metformin on metabolic measures. A small pilot trial of low-dose liraglutide plus metformin before IVF reported pregnancy rates per transfer of 85.7% versus 28.6% with metformin alone, despite similar weight loss. More recent data suggest improvement in endometriosis as well.