Guides
58 plain-English guides to GLP-1 medicines and peptides, grouped by what you're trying to do. Every number links to its source.
New here?Pick pen, vial, tablet or peptide, and see what to read first.GLP-1 dosing
Semaglutide, tirzepatide and others: dose steps, missed doses and changing your day.
- Missed a GLP-1 dose? The rule for each medicineHow late is too late depends on your medicine. Each US label sets its own window, and a few UK rules differ.7 min
- Tirzepatide dosage chart: mg, mL and unitsPrescriptions say mg and syringes say units. This chart lines up each Mounjaro and Zepbound label dose with its mL and U-100 units.8 min
- Semaglutide dosage chart: mg, mL and unitsPens give you a set dose in mg. If your semaglutide comes from a vial, each label dose also has to become mL and syringe units.9 min
- How to change your GLP-1 injection dayEvery weekly GLP-1 label lets you move your injection day. What changes between medicines is how long you must wait after your last dose.6 min
- Can you stay on a GLP-1 dose longer than 4 weeks?The labels set a shortest time on each dose, not a longest. A few also say what to do when a dose is hard to tolerate.6 min
Show all 16 glp-1 dosing guides
- Mounjaro pen doses in the UKEvery UK Mounjaro pen gives 4 fixed doses, and the liquid left at the end isn't a 5th.7 min
- Wegovy 7.2 mg: who it's for, how you step up, and what the trials showed7.2 mg is the highest Wegovy dose. You only get there after time on 2.4 mg, and the US and UK rules differ in a few places.8 min
- Restarting a GLP-1 after a breakOnly some GLP-1 labels say what to do after a long gap, and they don't agree on how long counts as long.6 min
- Foundayo dosage: dose steps, how to take it and missed dosesFoundayo is a once-daily GLP-1 tablet with six strengths. Each step lasts at least 30 days, and food doesn't matter.6 min
- The Mounjaro "golden dose": what the label, MHRA and Lilly saySome medicine is meant to be left in a Mounjaro KwikPen after the 4th dose. Every official source we checked says it isn't a 5th dose.5 min
- Retatrutide trial results: phase 2 and phase 3Retatrutide has produced some of the largest weight losses seen in obesity drug trials, but it isn't approved anywhere yet. These are the published numbers, dose by dose.8 min
- Saxenda dosage: daily steps, pen doses and missed dosesSaxenda goes up every week for 4 weeks, then stays at 3 mg a day. Here are the steps, what one pen covers, and the rules if you miss a day.6 min
- Trulicity dosage: dose steps, pens and missed dosesTrulicity (dulaglutide) is a once-weekly pen with four strengths. The US and UK labels start people differently, but the missed-dose rule is the same.6 min
- Oral semaglutide: Rybelsus and Wegovy tablet doses and how to take themSemaglutide tablets only work well if you take them the label's way: empty stomach, a little water, then 30 minutes before anything else. The doses differ by brand and country.7 min
- Can you get Wegovy or Mounjaro on the NHS?Yes, if you meet NICE's criteria, but the routes differ. Wegovy goes through specialist weight services, and Mounjaro is being opened up in GP surgeries group by group.7 min
- Zepbound vials vs pens: single-dose, multi-dose and KwikPen comparedZepbound now comes four ways in the US. The medicine and doses are the same in each. What changes is the volume, what else you need, and how long it keeps.6 min
Side effects and results
How common each side effect is on the label, and what the trials showed for weight.
- GLP-1 side effects: how common and how long they lastStomach trouble tops the side-effect list on every GLP-1 label, and most of it happens while the dose is going up.8 min
- GLP-1 weight loss by week: what the trials foundThe trials report averages at set checkpoints, and the spread around each average is wide.7 min
- GLP-1 constipation: how common it is, and when to get helpConstipation is one of the most common GLP-1 side effects, and it tends to hang around longer than nausea does.6 min
- GLP-1 sulfur burps: how common, and what's knownBurping is on every GLP-1 label, but none of them say anything about the smell.6 min
- GLP-1 hair loss: how common, and why women report moreHair loss is on the Wegovy, Zepbound and Foundayo labels, and in every label that splits it by sex, women reported far more of it than men.7 min
Show all 6 side effects and results guides
Mixing and syringes
Reconstitution, bac water and reading an insulin syringe.
- How to use a GLP-1 pen: flow check, hold time and what to do if no drop appearsMulti-dose pens need a test squirt and a new needle each time. Single-dose pens don't, but you have to hold them on the skin long enough. Each pen's instructions set the numbers.8 min
- How to reconstitute peptidesMixing (reconstituting) means adding bacteriostatic (bac) water to the freeze-dried powder in your vial so you can measure out doses. How much water you add, and how you add it, sets every dose that follows.8 min
- How much bac water to add to a peptide vialThere's no single right amount. The water sets how much peptide each unit on your syringe holds, so choose an amount that puts your dose on a line you can read.5 min
- How to read an insulin syringeThe numbers on the barrel are units of liquid, not milligrams of medicine. To read one correctly, check the scale, line up the top edge of the plunger with your number and clear any air.7 min
- Units vs mg vs mL: what's the difference on a syringe?Units and mL measure how much liquid is in the syringe. mg and mcg measure how much medicine is in that liquid. The vial strength links the two.6 min
Show all 13 mixing and syringes guides
- Cloudy peptide vial: shake or swirl, and when to throw it outFoam right after mixing is common and settles. A vial that stays cloudy, has flakes or has changed color is one that approved labels say not to use.6 min
- Bacteriostatic water vs sterile water vs salineAll three are sterile. The difference is the preservative: bacteriostatic water has one so a vial can be used more than once, and the other two don't.6 min
- U-100 vs U-40 vs U-500 syringes, and needle sizesThe number after the U tells you how much liquid each unit line holds, so a syringe from the wrong scale gives the wrong dose even when you read it perfectly.7 min
- GLP-1 injection sites and how to rotate themStomach, thigh and upper arm all work equally well for semaglutide and tirzepatide. Changing the exact spot each week is what the labels ask for.6 min
- How to draw a dose from a vial with an insulin syringeThe Zepbound and Mounjaro vial instructions, MedlinePlus and the CDC all describe the same short routine. The two habits that matter most are a new needle every time and checking for air.6 min
- How to dispose of needles and GLP-1 pens safelyUsed needles go straight into a sharps container, never loose in the bin. What happens to the full container depends on where you live.6 min
- mcg to mg: how to convert micrograms and milligramsThere are 1,000 micrograms in a milligram. Moving the decimal point three places is the whole conversion, and getting it wrong means a dose 1,000 times off.4 min
- How many doses are in a GLP-1 pen or a peptide vial?For a branded pen or vial, the label tells you, and it's usually 1 or 4. For a peptide vial, divide what's in the vial by the dose, and round down.6 min
Storage and travel
How long pens and vials last, in and out of the fridge, and flying with them.
- How long can GLP-1 pens stay out of the fridge?Anywhere from zero to 56 days, depending on the pen and whether you've used it yet. Every label caps room temperature at 30 °C (86 °F).6 min
- How long do reconstituted peptides last?Nobody has published tested numbers for research peptides once they're mixed. Approved peptides and GLP-1 pens do have exact label limits, and they vary a lot from product to product.8 min
- Traveling with GLP-1 pens and peptidesPens, needles and cooling packs are all allowed in your carry-on in the US and the UK. The harder part is the temperature, and the label sets that.7 min
- Left your pen or peptide out overnight, or it froze?A night on the counter is often within a GLP-1 pen's label. A frozen pen isn't, on any label. For research peptides, nobody has tested either.6 min
- The 28-day rule for bacteriostatic water, explainedIt's a limit on how long a pierced multi-dose vial can be used. It isn't printed on the bac water label, and it says nothing about the peptide you mix into it.6 min
Comparing and switching
Brand against brand, branded against compounded, and moving from one medicine to another.
- Ozempic vs MounjaroBoth are weekly injections, but the medicine inside is different. Each also has a sister brand for weight loss, Wegovy and Zepbound, compared here too.7 min
- Wegovy vs ZepboundOne is semaglutide, the other tirzepatide, and one trial has put them side by side.7 min
- Ozempic vs WegovySame medicine inside, but they're licensed for different things, go up to different doses and come in different pens.6 min
- Switching from semaglutide to tirzepatideMoving from Ozempic or Wegovy to Mounjaro or Zepbound isn't an mg-for-mg swap. The labels and pharmacy guidance below give you a starting point for the talk with your prescriber.7 min
- Mounjaro vs ZepboundSame medicine, same doses, same pens and vials. The difference is what each one is approved for, and in the UK there's only Mounjaro.5 min
Show all 7 comparing and switching guides
- Switching from tirzepatide to semaglutideMoving from Mounjaro or Zepbound to Wegovy or Ozempic usually means starting semaglutide from the bottom. The labels and pharmacy guidance below are a starting point for the talk with your prescriber.7 min
- Compounded vs branded GLP-1sCompounded semaglutide and tirzepatide aren't the same as Ozempic, Wegovy, Mounjaro or Zepbound. This covers what regulators have said, where things stand and the safety problems they've flagged.8 min
Safety and status
What regulators and studies say about peptides that aren't approved.
- CJC-1295 and ipamorelin: what FDA and anti-doping agencies sayYou might have seen them on social media or offered by a clinic. Neither is an approved medicine. These are the facts from regulators and the studies in people, both ways.6 min
- Is BPC-157 legal? Status by countryNo country has approved a medicine that contains BPC-157. What that means for you depends on where you live, and in the US the rules are still under review.7 min
- What “research use only” and a COA really meanThe label is a legal disclaimer, not a quality grade. A certificate of analysis tells you something about one batch of powder, but less than most people assume.7 min
- GLP-1s and birth control: does Mounjaro or Wegovy affect the pill?The tirzepatide labels carry a warning about the pill. The semaglutide labels don't. It matters most in the first weeks and after each dose increase.6 min
- GLP-1s and pregnancy: what each label saysNone of these medicines has enough data in pregnancy to know the risk, so the labels lean on animal studies and how long each drug stays in the body.7 min
Show all 8 safety and status guides
- Do you need to stop a GLP-1 before surgery?Not always. The rules changed in 2024, the labels don't give a stop date, and the decision sits with the people doing your procedure.7 min
- The GLP-1 thyroid cancer warning: what it says and what studies showThe warning comes from rats and mice. Whether it applies to people still isn't settled, and the US and UK labels handle it very differently.7 min
- Pancreatitis and gallbladder problems on a GLP-1: how common, and what to watch forBoth are listed as serious warnings on every GLP-1 label. Both are uncommon. The symptoms are worth knowing, because the early signs look like ordinary GLP-1 stomach upset.7 min
Research peptides
BPC-157, TB-500 and others: what studies used and their status.
- Peptide half-life chartHalf-life is how long it takes for half a dose to leave your blood. Every figure below names its source and says whether it was measured in people or only in animals.8 min
- BPC-157 vs TB-500They're often sold together, sometimes in one vial, but they're different peptides with very different amounts of evidence. Neither is FDA-approved.8 min
- GHK-Cu injectable vs topical: what's actually been studiedAlmost everything known about GHK-Cu in people comes from creams and serums on the skin. Injected GHK-Cu has been tested in rats, not in controlled human trials.6 min
Guides by compound
TirzepatideMounjaro, ZepboundSemaglutideOzempic · Wegovy · Rybelsus · compounded semaglutideRetatrutideLY3437943BPC-157Body Protection Compound 157, Bepecin, PL 14736TB-500Thymosin beta-4 fragment 17-23, Ac-LKKTETQGHK-CuCopper peptide · copper tripeptide · glycyl-L-histidyl-L-lysine copperNAD+Nicotinamide adenine dinucleotide · nadide · coenzyme I · NADLiraglutideSaxenda, VictozaOrforglipron (Foundayo)Foundayo