HbA1c lag and what it can and cannot tell you at eight weeks

HbA1c lag and what it can and cannot tell you at eight weeks Writing it up because I had to work it out twice and would rather nobody else did.

Something about hba1c lag does not reconcile and I would like a second pair of eyes before I decide which half is wrong.

Two sources, both reputable, giving figures that cannot both be right unless they are measuring different quantities. My suspicion is that they are, and I cannot see how.

Narrowing the opening post, because the general version has more than one answer.

Glycaemic markers integrate over different periods. A point glucose and a longer-term marker disagreeing is not a contradiction; it is two different questions.

I have left out the parts I could not verify.

The claim about hba1c lag upthread is stronger than its source supports. I have read the source. The source says "associated with" and the post says "causes".

Adding thanks rather than a view. I do not have a view worth the space.

An observation about hba1c lag that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.

Post #5 answers the question as asked. The question underneath it is different.

Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.

TSH and free hormones: TSH is a reasonable screening test but does not tell you about actual free hormone levels. If TSH is abnormal, free thyroid hormones confirm whether there is a real thyroid problem.

Posting it because the silence on this was starting to look like agreement.

If you are new and reading this thread for the answer to hba1c lag: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping.

Where the hba1c lag discussion usually stalls is that nobody wants to say "I do not know" and everyone is willing to say "it varies". Those are the same sentence with different clothes on.

The arithmetic in post #10 is right; the assumption feeding it is the part to check.

A trend needs at least three points to be a trend. Two points are a line and a line through noise is still a line.

It is worth stating the boring hypothesis before the interesting one.

Answering the question post #8 raises rather than the one it answers.

Two sentences on hba1c lag and then I will stop, because the rest is speculation and the thread is better without mine.

What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.

That is the distinction I keep failing to hold on to. Written down now.

I would be cautious about generalising from the hba1c lag example above. It is a good example. It is one example.