Half-life, steady state, and accumulation worked through posts 121–131
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Hepatic metabolism: the degree to which each compound is hepatically metabolised versus renally cleared is known but varies. Severe liver disease changes clearance.
post #122 answers the question as asked. The question underneath it is different.
Bioavailability: oral semaglutide has low bioavailability (roughly 1%) due to peptide instability. That is why the oral dose (14 mg) is so much larger than the injectable dose. Comparing them by mass is meaningless.
SNAC (the oral bioavailability enhancer): sodium N-(8-[2-hydroxybenzoyl]amino) caprylate transiently raises gastric pH and promotes absorption. Without it, oral bioavailability is too low for clinical use. With it, bioavailability is still variable between people.
Accumulation at steady state: with a week-long half-life, steady-state concentration is reached around 4 to 5 half-lives (about 4 to 5 weeks). Before that, concentration is rising with each dose. The clinical implication: escalating before 4 weeks means escalating before steady state.
I read post #124 twice before replying, because I had assumed the opposite.
Two things before anyone answers the substance.
First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.
Individual variation: people vary in how quickly they absorb, distribute, metabolise, and excrete these compounds. That variation is partly genetic and partly due to individual biology (gut motility, kidney and liver function). It explains why two people on the same dose have different response magnitudes.
Half-life: semaglutide ≈ 165–184 hours (about a week). Tirzepatide ≈ 5 days. Liraglutide ≈ 13 hours. The half-life determines how much accumulation happens at steady state and how long it takes to clear after stopping.
Picking up post #126: that is the part I would want checked first.
Fasting requirement for oral semaglutide: food and large fluid volumes reduce absorption. The fasting window (30 minutes before and 30 minutes after) is designed to maximise absorption. Violating it measurably reduces exposure.
Renal clearance: these compounds are cleared partly via the kidney. In severe renal impairment, clearance is slowed and accumulation risk is higher. Dose adjustments might be needed.
Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.
Suggested topics
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
Follow-up: Subcutaneous absorption kinetics and site differences
Subcutaneous absorption kinetics and site differences — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it anywhere. A…
|
4 | 9.9k | 10mo | |
|
Clearance pathways and what renal impairment changes
Clearance pathways and what renal impairment changes Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means before I repeat it…
|
+11 | 15 | 43k | 2mo |
|
Peak-to-trough ratio at steady state for a weekly agent — the long version
Peak-to-trough ratio at steady state for a weekly agent — the long version Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means…
|
+57 | 61 | 708 | 1d |
|
Time to steady state after a dose increase
On the subject in the title: Time to steady state after a dose increase Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front of me that…
|
+151 | 163 | 9.7k | 21mo |
|
[2026 update] Clearance pathways and what renal impairment changes
On the subject in the title: Clearance pathways and what renal impairment changes Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front…
|
+63 | 69 | 50k | 13mo |
Related topics — sharing the tags semaglutide, liraglutide, tirzepatide
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
Albumin binding and how it produces a long half-life
Albumin binding and how it produces a long half-life — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it anywhere. A…
|
+38 | 44 | 6.6k | 14mo |
|
Revisiting: GLP-1 receptor distribution: central and peripheral
Revisiting: GLP-1 receptor distribution: central and peripheral — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a…
|
+61 | 66 | 15k | 8mo |
|
Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly — the long version
On the subject in the title: Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly — the long version Working notes rather than a conclusion. Session topic: PIONEER 6 ( N Engl J Med ,…
|
+85 | 90 | 13k | 7mo |
|
Coming back to: Time to steady state after a dose increase
Time to steady state after a dose increase Writing it up because I had to work it out twice and would rather nobody else did. Posting the method first, because I know what the first three replies will…
|
+104 | 110 | 16k | 2d |
|
Titrating on tolerability rather than on the calendar
On the subject in the title: Titrating on tolerability rather than on the calendar Working notes rather than a conclusion. I have read the maintained page on this and I still have a gap, so I am asking rather…
|
2 | 31k | 13mo |