Here's what I learned going into Achilles surgery: the medical team doesn't know what you know about living in your body.

I had pointed conversations with my anesthesiologist about every medication that would touch my system. The nerve blocking agent, how it works between the nodes of Ranvier, shutting down sodium channels, and what that means for glucose in the hours after surgery. We mapped the duration against my basal insulin rates and planned a postoperative bolus to cover the gap. We talked through what the nursing team would have available for food postoperatively, and how the timing would line up with my normal insulin patterns.

I talked with the surgical team about the sleep and wake-up patterns in the post-operative spaces. With my pump in activity mode and my personal basal-bolus patterns mapped against their standard recovery timeline, everything seemed to match up, for a 30-minute procedure. But it could extend to 90 minutes depending on what they found once they went in. Planning for flexibility. As always with diabetes.

Every one of those conversations started because I asked. Not because someone on the team brought it up. They were wonderful, engaged, genuinely helpful once we got talking. But the starting was on me.

That's the thing about being a 35-year T1D patient in an orthopedic setting. You know things the surgical team doesn't expect you to know. And the medication interactions, the stuff this newsletter is about, that's exactly the knowledge gap where your advocacy isn't optional. It's what keeps you safe when you can't keep yourself awake.

That split-second calculation runs through your head before the nurse finishes her sentence. Do I explain? Will she understand? And underneath it all: I need to make sure someone knows this before I'm under anesthesia.

Here's the number that matters: 61 mg/dL.

That's how much your CGM can overread after a standard 1,000 mg dose of Tylenol. Not a little noise in the data. A full 61 points higher than your actual blood sugar, peaking about two hours after you take it.

Think about what that means. Your CGM says 220. You correct. Except your real blood sugar is 160. That "correction" just drove you toward a dangerous low.

It gets worse. The error persists for up to eight hours after a single dose. And in one documented case, a person's actual blood sugar was 46 mg/dL, severe hypoglycemia, while their CGM displayed 175 mg/dL. The sensor showed "fine" while the body was in crisis.

If you use a closed-loop system like Control-IQ or Loop, the algorithm sees that false high and increases your insulin automatically. No human decision required. Just silent, automated insulin delivery based on a number that isn't real.

The three pain med categories work completely differently:

Acetaminophen (Tylenol): The chemical structure fools your CGM sensor. The electrode can't tell the difference between Tylenol and glucose, so it reports both as sugar. Newer sensors (G6, G7) handle standard doses better, but IV acetaminophen in surgical settings still causes major misreadings.

NSAIDs (ibuprofen, naproxen): No CGM interference. These don't mess with your sensor. At high sustained doses, they can lower blood sugar slightly through insulin-related pathways, but the kidney risks with T1D usually make this a conversation for your endo.

Opioids (tramadol, oxycodone, morphine): Different problem entirely. Tramadol caused severe hypoglycemia in 46.8% of hospitalized T1D patients in one study. Nearly half. Opioids suppress your body's natural "save me from a low" response, the epinephrine surge, the glucagon release. When you're sedated, you won't feel the shaking or sweating. You won't wake to your CGM alarm.

Here's the twist that catches medical teams off guard: opioids typically raise blood sugar in people without diabetes, but lower it in people with diabetes. That inversion means providers don't expect what actually happens.

Your pain management plan needs to account for your diabetes technology. This isn't a nice-to-have conversation with your surgical team, it's a safety-critical one.

Most orthopedic teams don't know that Tylenol can fool your CGM. They don't know that tramadol can drop your blood sugar into the 40s while you're too sedated to notice.

The reframes that matter:

Before your surgery, have this conversation with your anesthesiologist AND your endocrinologist. Print this checklist or take a photo:

This checklist exists because of what went wrong for people who didn't have it. Use it.

This is exactly the kind of invisible complexity that families living with T1D face. Your CGM says one thing. Reality says another. Knowing the difference isn't just helpful, it's survival.

In BTD Guide 1: Surveillance to Support, we dig into how to turn diabetes data into actual understanding. Not just numbers, but what those numbers really mean. When to trust your devices. When to double-check. How to read between the lines of what technology tells you.

Because data literacy isn't abstract when you're heading into surgery tomorrow.

Has a medication ever thrown off your CGM readings? Did you catch it in time, or did you learn the hard way?

What's your "always pack the fingerstick meter" story?

This newsletter is part of the Better Together Through Recovery series, free content for the T1D community navigating injury recovery, surgery, and the unexpected complications that come with managing diabetes through it all.