Short answer: In the label's placebo-controlled trials, the most common Glucotrol XL side effects were dizziness (6.8% vs 5.8% on placebo), diarrhea (5.4% vs 0%), nervousness and tremor (3.6% each) and gas (3.2%). Of 580 people in trials, 3.4% had low blood sugar and 2.6% stopped because of it. Glucotrol XL has no boxed warning.
What Glucotrol XL is approved for: Glucotrol XL is a sulfonylurea approved, along with diet and exercise, to improve blood sugar control in adults with type 2 diabetes (section 1). It is not recommended for type 1 diabetes or diabetic ketoacidosis (section 1.1).
Source
GLUCOTROL XL (glipizide) extended release tablets, for oral use, prescribing information and Patient Information. Roerig (Pfizer). DailyMed, version published July 23, 2026. DailyMed setid eed99b60-d043-4249-9b2a-f05e46fb588d
No. The current Glucotrol XL label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Glucotrol XL.
| Adverse effect | GLUCOTROL XL (%) (N=278) | Placebo (%) (N=69) |
|---|---|---|
| Dizziness | 6.8 | 5.8 |
| Diarrhea | 5.4 | 0.0 |
| Nervousness | 3.6 | 2.9 |
| Tremor | 3.6 | 0.0 |
| Flatulence | 3.2 | 1.4 |
Pooled double-blind, placebo-controlled trials.
Low blood sugar: of the 580 people who took Glucotrol XL in trials, 3.4% had hypoglycemia (a reading under 60 mg/dL and/or symptoms) and 2.6% stopped for this reason. No placebo patients reported it.
Stomach and gut effects (nausea, vomiting, constipation, indigestion) occurred in less than 3%, more often than on placebo.
Hives occurred in less than 1.5% and may pass with continued use; the label says the drug is stopped if skin reactions persist.
Mild to moderate rises in ALT, LDH, alkaline phosphatase, BUN and creatinine have been seen; the link to glipizide is uncertain.
Reported after approval: abdominal pain, liver injury with jaundice, low blood counts and platelets, hemolytic anemia, low sodium (SIADH), rash, and gut irritation and bleeding with another drug in the same non-dissolving tablet design.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Glucotrol XL is not used by people allergic to glipizide, its ingredients, or sulfonamide derivatives.
Low blood sugar. All sulfonylureas can cause severe hypoglycemia, which can lead to unconsciousness, seizures, brain impairment or death. The risk is higher with other diabetes medicines, in older, frail or malnourished people, with kidney, liver, adrenal or pituitary problems, with too little food, hard exercise or alcohol. Warning signs may be weaker with nerve damage or beta-blockers.
Hemolytic anemia. In people with G6PD deficiency, sulfonylureas can break down red blood cells, and the label says to avoid Glucotrol XL in them. It has also been reported in people without known G6PD deficiency.
Heart-related deaths with sulfonylureas. In the older UGDP study, people on the sulfonylurea tolbutamide for 5 to 8 years had heart-related death rates about 2½ times those on diet alone. The label says this warning may apply to the whole class.
Bowel blockage. The tablet has a shell that does not dissolve. Blockage has been reported in people with known narrowing of the gut with another drug in this design, so the label says to avoid Glucotrol XL with severe gut narrowing.
From the Patient Information that comes with Glucotrol XL:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.