SGLT2 inhibitors need to be stopped before surgery because they can trigger a dangerous form of ketoacidosis that’s unusually hard to detect. Unlike typical diabetic ketoacidosis, this version occurs with normal or near-normal blood sugar levels, so neither you nor your medical team may recognize it until it becomes severe. The FDA recommends stopping most SGLT2 inhibitors at least 3 days before a scheduled surgery, and ertugliflozin (Steglatro) at least 4 days before.
The Core Risk: Ketoacidosis With Normal Blood Sugar
Diabetic ketoacidosis, or DKA, happens when the body starts breaking down fat for fuel at a dangerous rate, producing acids called ketones that make the blood too acidic. Normally, DKA comes with very high blood sugar, which acts as a red flag. SGLT2 inhibitors change that equation. Because these drugs work by flushing excess glucose out through your urine, blood sugar can stay below 250 mg/dL even while ketone levels climb to dangerous territory. This is called euglycemic DKA.
The combination is deceptive. Standard glucose checks look fine, so the usual alarm bells don’t ring. Meanwhile, the acid buildup in the blood can cause organ damage if it goes unrecognized. Euglycemic DKA is defined by the same dangerous acid levels as regular DKA (blood pH below 7.3, low bicarbonate) but with blood sugar readings that appear reassuringly normal.
Why Surgery Makes This Worse
SGLT2 inhibitors shift your metabolism toward burning fat and producing ketones even under normal circumstances. They raise glucagon levels, promote fluid loss, and increase the activity of stress hormones like cortisol and epinephrine. Under everyday conditions, your body can usually keep this in check. Surgery stacks several additional stressors on top of that baseline shift.
Fasting before surgery was the most frequently cited trigger in a systematic review of perioperative ketoacidosis cases, followed by the metabolic stress of surgery itself. When you stop eating, your body ramps up fat breakdown for energy. Combine that with dehydration from fasting, the physical stress response to being cut open, and the flood of stress hormones that accompanies any major procedure, and you have a perfect setup for runaway ketone production. More invasive surgeries and emergency operations carry higher risk than minor procedures.
In a study of 1,169 surgical patients taking SGLT2 inhibitors, 1.8% developed euglycemic DKA within 30 days of surgery. That number shifted dramatically depending on whether the drug was stopped in time. Patients who did not discontinue their SGLT2 inhibitor at least 3 days before surgery had a 6.5% incidence of euglycemic DKA compared to just 0.4% in those who stopped on schedule. Most cases were diagnosed within the first week after surgery, with nearly half appearing in the first 3 days.
How Long to Stop Before Surgery
The FDA’s guidance is straightforward: stop canagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance) at least 3 days before scheduled surgery. Ertugliflozin (Steglatro) requires at least 4 days. The extra day for ertugliflozin reflects its pharmacology, with a half-life that ranges from 11 to 18 hours and steady-state levels that take up to 6 days to fully establish. These drugs don’t just wash out of your system overnight. Their effects on kidney glucose handling and ketone metabolism persist beyond the point where the drug itself clears your blood.
If you’re taking a combination pill that includes an SGLT2 inhibitor (such as Synjardy, Glyxambi, or Qternmet), the same timeline applies. Check with your surgical team about which component of your medication is the SGLT2 inhibitor and when exactly to stop. For emergency surgeries where there’s no time to stop the medication in advance, the risk is higher, and your anesthesia team should be aware you’re on one of these drugs.
Symptoms to Watch For
The tricky part about euglycemic DKA is that checking your blood sugar won’t help you catch it. Your glucose readings may look perfectly fine while your body is becoming dangerously acidic. Instead, watch for these signs in the days after surgery:
- Nausea or vomiting that seems disproportionate to your recovery
- Rapid, deep breathing as your lungs try to compensate for acid buildup
- Generalized fatigue or malaise beyond normal post-surgical tiredness
- Abdominal pain not explained by the surgical site
- Fruity-smelling breath from acetone in your exhaled air
- Confusion or altered mental state
The absence of the classic DKA warning signs (excessive thirst and frequent urination) makes this easy to miss. Monitoring urine or blood ketones during your recovery period, especially if you feel unwell, is a far more reliable early warning system than glucose checks alone.
Managing Blood Sugar While Off the Medication
Stopping your SGLT2 inhibitor 3 to 4 days before surgery means your blood sugar may run higher than usual during that window. This is expected and generally preferable to the risk of ketoacidosis. Your surgical or primary care team may adjust your other diabetes medications or add short-term insulin coverage to keep glucose in a reasonable range during the perioperative period. Bring this up at your pre-surgical appointment so there’s a plan in place rather than trying to figure it out the day before.
When You Can Restart
After surgery, the general guidance is to wait until you’re eating and drinking normally before restarting your SGLT2 inhibitor. This isn’t just about being able to swallow a pill. Your body needs to be past the acute stress of surgery, adequately hydrated, and taking in enough carbohydrates that the metabolic conditions favoring ketoacidosis have resolved. For minor outpatient procedures where you’re eating dinner that same evening, the timeline is short. For major surgery requiring days of limited oral intake, the restart may be delayed considerably. Your care team will make the call based on how your recovery is going.