Situation: A 64-year-old woman is brought to a stroke-ready hospital with sudden right-sided weakness and slurred speech that began 90 minutes ago. She weighs 104 kg. Noncontrast computed tomography (CT) shows no hemorrhage, and the team plans intravenous (IV) alteplase for acute ischemic stroke. Before thrombolysis, the nurse checks her capillary blood glucose. What is the reason for this check?

Hypoglycemia can cause focal weakness and speech problems that look like a stroke. Glucose is the only laboratory test required before thrombolysis unless a bleeding disorder or anticoagulant use is suspected; deficits that resolve when low glucose is corrected are not treated with alteplase.

Why glucose is checked before alteplase

The priority before giving IV alteplase is to confirm that the patient’s focal neurologic deficits are truly caused by acute ischemic stroke rather than by a reversible metabolic condition. Hypoglycemia can present with unilateral weakness, dysarthria, or aphasia that is clinically indistinguishable from an acute stroke. If the low glucose is corrected and the deficits resolve, the diagnosis is a stroke mimic, and thrombolysis is not indicated because the risk of intracranial hemorrhage would be incurred without any benefit.

Capillary blood glucose is the only laboratory test that must be obtained before thrombolysis unless there is clinical suspicion of a bleeding disorder or current anticoagulant use. This reflects the fact that glucose is the one readily correctable metabolic cause of stroke-like symptoms that can be identified at the bedside within minutes.

The case report by Zhang et al. illustrates an important nuance: hypoglycemia-induced stroke mimic can occur even when the glucose is not dramatically low. Their patient presented with dysarthria at a glucose of 4.1 mmol/L (74 mg/dL), which is above the conventional hypoglycemic threshold, yet the neurologic symptoms were attributed to a relative drop in glucose after intensification of glucose-lowering therapy ^[2]. This reinforces why the glucose value must be interpreted in the context of the patient’s baseline and recent medication changes, not just against a single cutoff.

Option	Why it is incorrect
1. High glucose is an absolute contraindication	Hyperglycemia is common in acute stroke and is associated with worse outcomes, but it is not an absolute contraindication to alteplase. The NINDS-derived exclusion criteria focused on hemorrhagic risk, not glucose elevation [1].
2. Alteplase is mixed in dextrose	Alteplase is reconstituted with sterile water, not dextrose. Dextrose-containing solutions can inactivate the drug, so they are avoided, but this is unrelated to the pre-treatment glucose check.
3. Glucose decides the alteplase dose	The alteplase dose is calculated from actual body weight (0.9 mg/kg, maximum 90 mg), not from the glucose level. This patient weighs 104 kg, so the dose would be capped at 90 mg.

Watch out! A glucose value in the normal or mildly low range does not automatically rule out a stroke mimic. The clinical picture must be reassessed after glucose correction; if deficits persist, ischemic stroke remains the working diagnosis and alteplase may proceed if the patient still meets time and eligibility criteria ^[2].

Key point! The purpose of the glucose check is to identify and treat hypoglycemia as a reversible stroke mimic before exposing the patient to the bleeding risk of thrombolysis. The overarching principle of acute stroke care remains “time is brain,” and rapid restoration of cerebral blood flow is the goal once hemorrhage and mimics are excluded .