Short answer: Low blood sugar (hypoglycemia) is the most common Basaglar side effect, as with all insulin. In the label's Basaglar trials, infection affected 24% and nasopharyngitis 16% of adults with type 1 diabetes, and 17% and 6% with type 2. Severe low blood sugar affected 4% in type 1 at 52 weeks and 1% in type 2 at 24 weeks. Basaglar has no boxed warning.
What Basaglar is approved for: Basaglar is a long-acting insulin approved to improve blood sugar control in adults and children with type 1 diabetes and in adults with type 2 diabetes (section 1). It is not recommended for treating diabetic ketoacidosis.
Source
BASAGLAR (insulin glargine) injection, for subcutaneous use, 100 units/mL, prescribing information, Patient Information and Instructions for Use. Eli Lilly and Company. DailyMed, version published August 10, 2026. DailyMed setid 0ad21db3-2b1c-4ed9-a687-bdd6a74d0aae
No. The current Basaglar 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 Basaglar.
| Adverse reaction | BASAGLAR + insulin lispro, % (n=268) |
|---|---|
| Infection | 24 |
| Nasopharyngitis | 16 |
| Upper respiratory tract infection | 8 |
Basaglar with insulin lispro; the table has no comparator column. "Infection" means infections other than nasopharyngitis or upper respiratory tract infection. Mean exposure was 49 weeks.
| Adverse reaction | BASAGLAR + oral antidiabetic medication, % (n=376) |
|---|---|
| Infection | 17 |
| Nasopharyngitis | 6 |
| Upper respiratory tract infection | 5 |
Basaglar with oral diabetes medicines; no comparator column. Mean exposure was 22 weeks.
| Adverse reaction | Another insulin glargine product, % (n=514) | NPH, % (n=503) |
|---|---|---|
| Hypertension | 20 | 19 |
| Sinusitis | 19 | 18 |
| Cataract | 18 | 16 |
| Bronchitis | 15 | 14 |
| Back pain | 13 | 12 |
| Cough | 12 | 7 |
| Urinary tract infection | 11 | 10 |
| Diarrhea | 11 | 10 |
| Depression | 11 | 10 |
| Headache | 10 | 9 |
This trial used another insulin glargine 100 units/mL product, not Basaglar itself, against NPH insulin.
| Measure | Another insulin glargine product (N=6231) | Standard care (N=6273) |
|---|---|---|
| Percent of patients | 6 | 2 |
Another insulin glargine 100 units/mL product against standard care, median follow-up 6.2 years.
Severe symptomatic low blood sugar on Basaglar: 4% of people with type 1 diabetes at 52 weeks and 1% with type 2 diabetes at 24 weeks. In a trial of another insulin glargine 100 units/mL product in children aged 6 to 15 with type 1 diabetes, it was 23% at 26 weeks.
Table 4: in a 28-week trial of another insulin glargine product in children with type 1 diabetes, rhinitis occurred in 5% on glargine (n=174) and 5% on NPH (n=175).
Redness, local swelling and itching at the injection site have occurred and were usually self-limiting. Severe whole-body allergy (anaphylaxis) has been reported. Swelling from sodium retention, skin pits or thickening (lipodystrophy) and weight gain can also occur.
In a 52-week type 1 study, 42% on Basaglar tested positive for anti-drug antibodies at least once (17% at baseline, 25% developed them). In a 24-week type 2 study, 17% did (5% at baseline, 12% developed them). The label says there was no evidence the antibodies affected efficacy or safety.
Reported after approval: other insulins, especially rapid-acting ones, given by mistake instead of insulin glargine; and localized cutaneous amyloidosis (lumps under the skin) at injection sites, which has affected blood sugar control.
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. Basaglar is not used during an episode of low blood sugar, or by people allergic to insulin glargine or its ingredients.
Never share a pen. A Basaglar pen is never shared between people, even if the needle is changed, because of the risk of passing on blood-borne infections.
Changes in insulin regimen. Changing insulin strength, maker, type, injection site or method can cause high or low blood sugar, so changes are made under close medical supervision with more glucose checks.
Low blood sugar. Hypoglycemia is the most common reaction to insulin, and severe episodes can cause seizures or death. Basaglar's long action may delay recovery from a low. Awareness of lows may be reduced with long diabetes, nerve damage, beta-blockers or repeated lows.
Medication mix-ups. Mix-ups between insulin products have been reported, so the insulin label is checked before each injection.
Serious allergic reactions. Severe, life-threatening whole-body allergy, including anaphylaxis, can occur; Basaglar is stopped if it does.
Low potassium. All insulins shift potassium into cells and can cause low potassium, which untreated can cause breathing paralysis, heart rhythm problems and death.
Heart failure with TZDs. Thiazolidinediones (such as pioglitazone) with insulin can cause fluid retention that may lead to or worsen heart failure.
From the Patient Information that comes with Basaglar:
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.