You forgot yesterday’s dose. Or you are three days past the weekly one. The question is always the same — take it now, skip it, or double up? — and the answer is almost never found by looking up the compound. It is found by looking up the compound’s half-life, because the half-life is the only thing in this question that does any work.
Organise your thinking by half-life class and the whole problem collapses into three cases. Organise it by compound and you will be memorising thirty answers to a question that only has three.
Class 1: half-life in minutes
CJC-1295 no-DAC (Mod GRF 1-29), ipamorelin, GHRP-2, GHRP-6, hexarelin, gonadorelin.
These are gone almost as fast as they arrive. Circulating levels are back to baseline long before the next scheduled dose, which means nothing accumulates. There is no reservoir, no steady state, no level to protect.
The consequence is unusually clean: a missed dose is a missed pulse, and that is the whole story. You did not get that pulse. You will get the next one. Nothing carried over, nothing is now off, nothing needs correcting. Skip it and carry on with the schedule as if the miss never happened.
The one thing not to do is take it late and then take the next one on schedule shortly after — that is two pulses close together, which is a different stimulus, not a repair of the first one. And doubling makes no sense at all here: doubling the size of a pulse does not retroactively create the pulse you missed. It just makes one bigger pulse.
Class 2: half-life in hours
BPC-157, TB-500, GHK-Cu, and most daily-ish peptides.
Here there is some carryover but not much. The compound is present for a meaningful fraction of the dosing interval, so being a few hours late barely shifts anything.
Take it when you remember, and continue on your normal schedule. If it is close enough to the next dose that the two would land nearly on top of each other, skip the missed one — stacking them close together delivers a spike you did not intend, and the point of daily dosing is regular exposure, not total mass shovelled in.
This class produces the fewest genuine questions and the most unnecessary anxiety. A late BPC-157 dose is not an event.
Class 3: half-life in days — the counterintuitive one
Semaglutide ~1 week. Tirzepatide ~5 days. Retatrutide ~6 days. Cagrilintide ~7-8 days. Eloralintide ~13-15 days.
This is where people worry most and where they have the least to worry about, and the reason is the thing that makes weekly dosing possible in the first place: these compounds accumulate. Each dose lands while most of the previous ones are still circulating. By steady state, the level in you at any moment is the sum of several doses, not one.
Which means: one missed weekly dose barely moves the level. Not “is survivable” — barely moves it. The dose you skipped was only ever contributing a fraction of what is present.
Run the arithmetic across the class. Two days past due, this is how much is still there:
Single-compartment decay from the trough. Longer half-life, smaller drop.
Two days late on eloralintide costs you under 10%. Two days late on tirzepatide — the shortest half-life in the class — costs you about a quarter. Neither is a crisis, and the ranking is exactly what the half-life predicts. If you want to see the shape rather than the numbers, the half-life plotter draws the decay and accumulation curves for any half-life and interval you enter, and the half-life chart lists the figures across compounds side by side.
A full missed week is bigger but still not dramatic. At a one-week half-life, skipping an entire dose and taking the next one on schedule means the level halves before it comes back up — noticeable, temporary, self-correcting within a couple of doses as accumulation rebuilds. You are not starting over.
The real risk is the fix, not the miss
Here is the part worth actually remembering.
For long half-life compounds, the missed dose is not the dangerous event. Doubling up to catch up is.
The logic that makes doubling feel right — “I’m one dose behind, so I owe one dose” — is exactly backwards for an accumulating compound. You are not behind by a dose. You are down by whatever fraction decayed, which the chart above says is usually small. Meanwhile the double dose does not fill a hole; it stacks on top of everything still circulating. You arrive at a peak level you have never been at before, held there for days, because the half-life that buffered your miss now buffers your overshoot with exactly the same patience.
The same asymmetry applies to Class 1 and Class 2, just with less at stake. In every class, the answer to “how many doses should I take?” is one.
The decision, in one pass
| Half-life class | Examples | Missed or late |
|---|---|---|
| Minutes | Mod GRF 1-29, ipamorelin, GHRPs, gonadorelin | Skip it. It was a pulse; you missed the pulse. Resume schedule. |
| Hours | BPC-157, TB-500, GHK-Cu | Take it when you remember. Skip if it crowds the next one. |
| Days | Semaglutide, tirzepatide, retatrutide, cagrilintide, eloralintide | Take one dose. Resume the normal schedule. The level barely moved. |
And across all three rows, the same footer: never double.
Frequently Asked Questions
What should I do if I miss a weekly peptide dose?
Take one dose and return to your normal schedule. Because weekly compounds accumulate, a single miss removes only a fraction of what is circulating — at a one-week half-life, being two days late costs about 18% of the level. The miss is small and self-correcting. What is not small is doubling up, which stacks a full extra dose on top of everything already there.
Can I double my next dose to make up for a missed one?
No. On an accumulating compound, doubling does not fill a hole — it adds a full dose on top of a level that was already near steady state, and the long half-life then holds you at that overshoot for days. The missed dose costs a fraction; the correction costs a whole dose. In every half-life class, the right number of doses to take is one.
Does a missed ipamorelin or CJC-1295 dose matter?
Barely. These have half-lives measured in minutes and nothing accumulates between doses, so a missed dose is simply a missed pulse — there is no level to protect and nothing carried over to correct. Skip it and continue on schedule. Taking it late and then dosing again shortly after just delivers two pulses close together, which is not a repair.
How late is too late for a peptide dose?
It depends entirely on the half-life relative to the dosing interval. For minute-scale compounds, any meaningful delay means you have simply missed that pulse. For hour-scale dailies, take it unless it would crowd the next dose. For day-scale weeklies, days of lateness move the level by single or low double digit percentages — being late is genuinely close to a non-event.
Why does half-life decide the answer instead of the compound?
Because everything the question turns on — whether the compound accumulates, how much is present when you are late, how much a doubled dose stacks — is set by the half-life. Compounds with similar half-lives behave the same way regardless of what they do pharmacologically. Learning three classes replaces learning thirty compounds.
Related reading
- Peptide Half-Life Explained — the concept underneath all of this
- Half-Life Plotter — draw the decay and accumulation curves yourself
- Half-Life Chart — the figures across compounds, side by side
- Peptide Dosing 101 — the fundamentals a dosing schedule sits on