Diabetes, A1c and Joint Replacement

The short answer

If you have diabetes and you are considering a hip or knee replacement, the number that matters is your A1c.

Diabetes itself is not the obstacle. Control is. A well-managed diabetic patient at 6.8 is in a better surgical position than someone sitting at 8.5, and plenty of diabetic patients have excellent joint replacements.

What A1c actually measures

A1c is not your blood sugar today. It is a measure of your average glucose control over roughly the past three months, which is why it is the number surgeons use — it describes the environment your body has actually been operating in, not a single morning reading.

For reference:

This three-month window has a practical consequence that catches people out, and it is covered below: you cannot fix an A1c in the weeks before surgery.

Why it changes your risk

The concern is infection, and specifically infection of the implant itself.

As A1c climbs, the rate of infection after joint replacement climbs with it, and the overall risk of complications rises considerably. Elevated blood sugar impairs wound healing and blunts the immune response — the two things you are most relying on in the weeks after an implant goes in.

Where my thresholds sit

Being specific is more useful to you than being vague, so here is exactly how I work.

Under 7 — the target

This is where I would like every patient to be. It is the number most commonly recommended, and it is the range where diabetes stops meaningfully changing your surgical risk.

Under 7.5 — my working cutoff

In practice this is my soft cutoff. If your A1c is under 7.5, I will proceed and I am comfortable doing so.

7.5 to 8 — the discussion

This is the borderline zone, and it is genuinely patient-specific. I want to be honest that the majority of patients above 7.5 I would not operate on. But some I would, and the next section explains who.

Above 8 — a hard no

Above 8 I am not willing to accept the risk. That is not a permanent refusal and it is not a judgement — it is a sequence. Patients who bring their A1c into range go on to have their surgery.

The 7.5 to 8 conversation

Everything in medicine is a weighing of the risk of a complication against the benefit of the operation. In this range, that weighing becomes a real conversation rather than a rule.

What moves me toward proceeding:

When all three are true, I will sometimes say plainly: we are accepting a slightly higher risk of infection in order to fix a problem that is doing real damage to your life. That is a decision made together, with the risk stated out loud — not a rule applied without looking at the person.

Why this is different from weight

This is worth understanding if you have also been told to lose weight, because the two are not treated the same way.

In June 2025 the American College of Rheumatology and the American Association of Hip and Knee Surgeons published a guideline in Annals of Internal Medicine that conditionally recommends against delaying surgery solely to reach a target BMI — but which explicitly continues to support delaying surgery for poorly controlled diabetes and for active nicotine use.

So the professional guidance has moved toward flexibility on weight while holding firm on glycemic control. That is not arbitrary — the evidence linking poor diabetic control to infection is stronger. If you are working on both, this is covered from the other side in BMI and joint replacement.

How to actually move the number

The single most useful thing to understand: plan on about three months to see meaningful change. Because A1c averages roughly ninety days, no amount of careful eating in the fortnight before surgery will shift it.

Which means the work starts when you begin thinking about a joint replacement, not when a date gets booked.

GLP-1 medications

These deserve their own mention because so many patients are now on them, and because they are unusually well suited to this particular problem.

GLP-1 medications were developed for diabetes and are also widely used for weight management. That combination means they often address both of the things standing between a patient and surgery at once — bringing the A1c down while producing meaningful weight loss. They have made preoperative optimization achievable for patients who genuinely struggled before.

If you were told no

Being told your A1c is too high, with no explanation of what the number needs to be or how long it should take, is a frustrating place to be left.

The answer here may genuinely be that we work on it first — this is one of the places I hold a fairly firm line, and the guidelines back it. But you should leave with a target, a timeline, and a plan rather than a closed door.

If you would like a second view on where you actually stand, a second opinion is a reasonable thing to seek. Bring your recent labs and your X-rays and you will get a straight answer.