CommunityBloodwork & Biomarkers

A1C went up

18 replies7 peopleFeb 16, 2026☆ Follow
Summary

why did A1C rise after surgery while fasting glucose stayed low on tirzepatide

The original poster saw fasting glucose at 66 but A1C climb from 5.6 to 5.9 after stopping the medication for surgery recovery. Others noted that A1C reflects a weighted average over months while a single fasting reading captures only one moment, and surgical stress or medications could have raised prior averages. Several participants viewed both numbers as still acceptable and suggested tracking fasted insulin or using a CGM for clearer data instead of chasing lower A1C alone.

What this discussion establishesWhere people disagree

Some see any A1C above 5.7 as worth addressing while others treat 5.9 as no concern when fasting glucose is low and prior numbers were worse

Still open

whether the current dose is still effective or should be adjusted after the recent break

Nothing here is advice.

18 replies · 7 people
WrySparrow63archiveopening postFeb 16

I just received lab work from blood taken on Friday. Fasting glucose came back at 66 yet A1C rose to 5.9 from 5.6. I stay hungry but keep portions controlled so I do not regain weight. I am questioning whether the tirzepatide I take is still effective. How can fasting glucose sit so low while A1C climbs? I currently use roughly 6 to 8 mg weekly for maintenance. I paused it for four or five weeks around surgery because the surgeon required stopping two weeks before and several weeks after the procedures.

SharpCinder28archiveFeb 16

That combination is odd even after a month off. I paused for a month last October and my A1C kept falling. Maybe the stress from surgery plus the time without medication played a role, or perhaps the surgery itself created a falsely elevated reading. With your fasting glucose that low your current dose seems more than enough if anything.

WrySparrow63archiveFeb 16
↳ replying to @SharpCinder28

Interesting. I reduced my dose today to around 4 mg. I had already injected before seeing the lab email. I should look for any test results from the batch I used but I never checked that specific one.

SlowLedger42archiveFeb 16
↳ replying to @WrySparrow63 (opening post)

Many factors could explain it. Fasting glucose only shows your metabolic state on that particular day. A reading of 66 is quite good. It also raises the possibility that the dose might be higher than needed. A1C instead shows average red blood cell glycation over recent months, weighted more toward the later weeks. The simplest explanation is that recent levels were low while earlier ones were higher. Surgery could have involved medications that raise blood sugar such as steroids. It is like wondering why weight did not drop dramatically after one day without food. One number is a snapshot and the other is a longer average.

WrySparrow63archiveFeb 16
↳ replying to @SlowLedger42

Thanks. I plan to follow up with my doctor though she always wants an in-person visit. I am four months post-op now. Since A1C covers the last three months I have been back on the medication consistently for at least that long. I continued it specifically for A1C control and now that number rose so I am unsure what to make of it. Without the medication my morning strip readings sat in the 120s and sometimes reached 130. I had never seen the 60s before. Earlier labs were just under 100 and my own checks usually show around 95. I will ask my NP about a CGM. My dietitian had a program with one so I could contact her too. After spending so much on surgery to remove loose skin I am focused on avoiding any weight regain.

SharpCinder28archiveFeb 16
↳ replying to @WrySparrow63

That explains it. Your current medication appears to be working well if not better than expected.

WryLedger88archiveFeb 16
↳ replying to @WrySparrow63 (opening post)

An A1C test measures average blood glucose over the past two to three months. It shows the percentage of hemoglobin that has sugar attached and reflects the typical lifespan of red blood cells. Tests are usually done every three to six months for diabetes management. The three-month window exists because red blood cells last about that long before being replaced.

SlowLedger42archiveFeb 16
↳ replying to @WrySparrow63

You might be comparing a later blood draw to a morning strip result. Dawn phenomenon often raises the early morning number. Both 5.6 and 5.9 remain acceptable given your earlier higher readings. Lab machines also have some imprecision so a 0.1 to 0.2 difference could be error and the values might actually be the same. If the goal is optimal rather than adequate numbers then tracking fasted insulin over time would be more informative than A1C once it is already near normal.

SlowLedger42archiveFeb 16
↳ replying to @WryLedger88

These chatbots sometimes get basic conversions wrong yet people treat the rest of the output as reliable.

WryLedger88archiveFeb 16
↳ replying to @SlowLedger42

Does that make the information wrong? I am not a doctor. I shared the AI text because it matched what I already thought was accurate.

SharpCinder28archiveFeb 16
↳ replying to @SlowLedger42

My own dawn phenomenon lined up closely with my A1C so the medication helped across the board. Five point nine is not a problem. When mine reached 6.1 just before starting the medication my doctor viewed pre-diabetes as something minor since he was already prescribing for weight. He paid far more attention to lipids though. Everyone seems to have a different focus with lab results.

SlowLedger42archiveFeb 16
↳ replying to @WryLedger88

Everything else the chatbot said was accurate. The only odd part was the month-to-days conversion. Two to three months is roughly sixty to ninety days and that does not require medical training to know.

SlowLedger42archiveFeb 16
↳ replying to @SharpCinder28

The slight increase in daily insulin release from these medications can blunt the dawn phenomenon. A CGM makes that effect visible quickly. The body normally mounts a strong first-phase insulin response to food but a weaker one to liver glucose output. In the morning after many hours without eating cortisol prompts the liver to release glucose and the insulin response often undershoots so levels rise temporarily. That pattern itself is not harmful.

SharpCinder28archiveFeb 16

With a CGM what post-meal number after carbs counts as less than ideal and how long should any spike last?

SlowLedger42archiveFeb 16
↳ replying to @SharpCinder28

That question is still debated and no clear answer exists. Many people focus on it more than necessary. How fast the spike returns to baseline and how it compares with other people's responses probably matters more. A large spike from white rice might reach 200 yet drop back within ninety minutes to two hours. After major weight loss the same meal might produce a shorter spike. Some argue anything over 140 is undesirable but the evidence for that is not strong. A spike that stays high for hours instead of clearing quickly would point to greater insulin resistance.

PatientAnchor11archiveFeb 16
↳ replying to @SlowLedger42

Using a CGM taught me more about type 2 diabetes than any other source. I recommend trying one at least briefly.

BrightBeacon35archiveFeb 16

Berberine might offer some help.

LevelTimber64archiveFeb 17

This thread is useful. I have labs tomorrow morning for the first time since switching sources. I see my doctor next week. I expect my A1C to match the result from six months ago. All else equal I pay less attention to single glucose readings than to A1C.

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