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Extreme tiredness right after beginning Reta

16 replies14 peopleApr 29, 2026☆ Follow
Summary

Why does starting retatrutide cause sudden extreme fatigue and sleepiness, and how long does it usually last?

Users report that strong daytime drowsiness often appears within the first days on Reta or similar GLP-1 drugs and tends to peak for a few weeks before easing into milder afternoon slumps or disappearing after one to two months. Individual reactions differ sharply even at the same low starting dose, with appetite suppression sometimes absent until higher amounts are reached. Several note that fatigue improves once the body adapts or calorie intake stabilizes, though a few still feel lower energy months later.

What this discussion establishesWhere people disagree

Whether to increase the dose while fatigue is still strong or to remain at 1 mg until symptoms ease

Still open

What reliably counters ongoing low energy levels after the initial adaptation period

Nothing here is advice.

16 replies · 14 people
SteadyCinder74archiveopening postApr 29

My partner began Reta at 1 mg the day before and reports no change in hunger or anything else except intense exhaustion and drowsiness that makes staying awake during daylight hours nearly impossible. This is nothing like what I went through myself. Has anyone else run into this and if so how long did it continue? I doubt she will put up with it much longer. Calories are not lacking; if anything she is eating more than she did before starting.

GreenMeadow54archiveApr 29

The first week on Tirz felt identical for me. It is a typical response to these GLP medicines and usually fades for most after seven to fourteen days. Reta does not curb appetite as strongly as Tirz so many people say they do not notice that part until they reach higher amounts.

PlainAlder11archiveApr 29

This medication needs time to work and is not instant. The amount she is on might simply be too low. My wife and I began at 2 mg for four weeks before moving higher. I have no idea about the tiredness though. Neither of us dealt with that.

SlowLedger42archiveApr 29
↳ replying to @SteadyCinder74 (opening post)

I went through the same thing. The worst part lasted roughly two days but it took a good month or two before everything felt normal again. It makes sense she would eat more while feeling that way yet once the scale begins to move I expect it will become more motivating. As the exhaustion shifts from severe to just mildly annoying it should also become less of an obstacle, similar to recovering from a flu where you can tell you are improving even if not fully back to normal.

NorthKettle44archiveApr 29

I agree the sleepiness can reach near narcoleptic levels for some and is normal plus temporary. For me the strongest phase lasted only a few weeks and hit hardest a day or so after each injection. That intensity later settled into a brief low-energy dip in the afternoon before becoming normal overall. Months later if the tiredness returns it usually means I need to eat more.

LevelWillow41archiveApr 29

I dealt with major tiredness when I first started and figured it came from dropping from three to five thousand calories daily down to around one thousand. It affected everything including very half-hearted workouts. Over a couple of months it gradually improved and returned to normal.

PatientSparrow67archiveApr 29
↳ replying to @SteadyCinder74 (opening post)

That amount is quite low. I would raise it to at least 2 mg for one week then 4 mg the week after. Eating enough protein and carbs matters when using reta.

BlueQuill24archiveApr 29

I also get fatigue along with sleepiness and dry mouth. It appears to lessen as time passes.

SteadyCinder74archiveApr 29

Thanks for the helpful replies. She already feels more optimistic that this will improve. We will wait until the end of this first week to see how she feels before considering any increase. It still surprises me how much experiences differ. A tiny dose affected me strongly and I had to work at eating enough calories yet I had no major tiredness.

CopperBeacon48archiveApr 29

Encourage her to continue. I noticed changes within forty-eight hours while my dad on the same vial felt nothing for two or three weeks. Once she begins to sense the effects and the weight starts coming off the motivation should increase. Hang in there; both of you have plenty of support here.

IronLantern24archiveApr 29
↳ replying to @SteadyCinder74 (opening post)

I experienced the identical situation when I began reta in January. Normally I have insomnia yet for the first couple of months all I did was sleep and I would doze off easily especially in the afternoon. Eventually it disappeared and now I only feel exhaustion when I raise the dose and it passes quickly. My energy still is not where I would prefer and I continue looking into ways to improve it.

RustKettle37archiveApr 29

My fatigue was fairly severe and eased after a few weeks yet my flat mood worsened over several weeks and stayed that way until I stopped the medication for a couple of weeks. I disagree with raising the dose while side effects are present. Splitting 1 mg twice weekly worked best for me. When I skipped a dose to try 1.5 mg once a week I became very ill the next day once it took effect. Even with good appetite control and slow scale movement I saw no visible changes and my pants fit the same for about six weeks. Then one morning I looked in the mirror and it seemed like the weight had suddenly melted away. Low and slow worked better for me.

NorthCompass23archiveApr 30
↳ replying to @NorthKettle44

I agree with that description exactly. It always hits a couple of days after the dose. It finally stopped after the first few weeks. Now at six weeks if I feel overly tired it is usually because I am under-fueled and I drink a fairlife shake.

AmberMeadow80archiveApr 30

I am six weeks into Reta and running an average eight-hundred-calorie daily deficit. I feel tired constantly. My sleep is good largely because I stopped drinking alcohol yet I still fall asleep on the couch an hour earlier than usual. A few other factors are in play: work is demanding right now both mentally and sometimes physically and my workouts are more frequent and harder than before Reta.

SlowLantern46archiveMay 1

I started at 6 foot 5 and 240 pounds and am now 227. I have been on 0.5 mg for a month. My intake went from over twenty-five hundred calories down to two thousand or less with high protein and low carbs while tracking and weighing everything. I added gym and cardio. Energy is higher for sure though sleep is worse. Everyone reacts differently. All I want from reta is better control over eating without nausea, just some level of indifference. I had a great meal last night but could have skipped it.

SteadyCinder74archiveMay 2
↳ replying to @AmberMeadow80

I only wish I could manage more intense workouts. Since my last injury my steady progress has shifted to frequent long breaks and sometimes dropping weights. I hope this changes once my system adjusts.

AmberMeadow80archiveMay 2
↳ replying to @SteadyCinder74

My main activities are rock climbing and yoga. Both become easier with less body fat. As the weight has come off I have been able to push harder at these exercises.

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Extreme tiredness right after beginning Reta · ZyraTrack Community