What is the most common side effect of labetalol?

October 10, 2025 •

4 min read

According to clinical trial data, approximately 11% of patients taking oral labetalol experience dizziness, making it the most frequently reported adverse effect. This means that for those wondering what is the most common side effect of labetalol, the answer for the tablet form is dizziness.

Quick Summary

Dizziness is the most common side effect of oral labetalol, while orthostatic hypotension is most common with the intravenous form. Fatigue, nausea, and headache are also frequent adverse effects, which often diminish as the body adjusts to the medication.

Key Points

Oral Labetalol's Most Common Side Effect is Dizziness: Approximately 11% of patients experience dizziness when taking labetalol tablets, most often when first starting the medication.
IV Labetalol's Primary Concern is Orthostatic Hypotension: The intravenous form of labetalol most commonly causes a sudden, significant drop in blood pressure upon standing, a condition known as orthostatic hypotension.
Fatigue and Nausea are also Frequent: Besides dizziness, patients may experience tiredness (fatigue), which affects about 5% of users, and nausea (6%).
Side Effects Often Diminish Over Time: Many of the common side effects, such as dizziness and fatigue, are temporary and lessen as the body gets used to the medication.
Serious Side Effects Require Immediate Attention: While rare, symptoms of liver injury, heart failure, or severe breathing issues warrant immediate medical contact.
Abrupt Discontinuation is Dangerous: Patients should not suddenly stop taking labetalol, especially those with heart conditions, as it can worsen symptoms and increase the risk of heart attack.

Labetalol is a unique prescription medication used to manage hypertension, or high blood pressure. It functions as both an alpha-blocker and a non-selective beta-blocker in a single substance, which is an important aspect of its pharmacology. This dual action helps to lower blood pressure by widening blood vessels and slowing the heart rate. While generally well-tolerated, understanding the potential adverse effects is crucial for patients and healthcare providers.

The Most Common Side Effects of Oral Labetalol

When taken in tablet form, dizziness is the most common side effect reported by patients. In clinical trials, 11% of patients experienced drug-related dizziness. This can be attributed to the medication's blood pressure-lowering effect. As the body adjusts to the medication, this sensation often lessens over time. In addition to dizziness, several other common side effects have been identified:

Fatigue and tiredness: Feeling tired or weak is another frequently reported side effect (5% incidence). Like dizziness, it typically improves as the body adapts.
Nausea: Approximately 6% of patients in clinical trials experienced nausea. Taking the medication with food can sometimes help manage this.
Headache: Headaches were reported by 2% of patients and are usually short-lived.
Stuffy nose: Nasal stuffiness (3% incidence) is a less common but still reported side effect.
Scalp tingling: Some people report a tingling sensation in their scalp or skin, particularly when first starting the medication.
Sexual dysfunction: This can include difficulty with ejaculation or erectile dysfunction.

Orthostatic Hypotension: A Key Concern with IV Labetalol

While dizziness is the most common issue for oral labetalol, a specific and significant side effect—orthostatic hypotension—is the most common for the intravenous (IV) formulation. In clinical trials for IV labetalol, almost 60% of participants experienced a sudden drop in blood pressure when sitting up or standing too quickly. This is because labetalol's alpha-blocking activity causes vasodilation, which can be more pronounced and sudden when administered intravenously. Patients receiving IV labetalol in a hospital setting should be kept in a supine position and their ability to tolerate an upright position must be carefully established before they are allowed to stand or ambulate. Orthostatic hypotension can lead to falls and injury, making careful patient monitoring essential.

Comparison of Side Effects: Labetalol vs. Selective Beta-Blockers

Labetalol's dual alpha- and beta-blocking mechanism gives it a different side-effect profile compared to selective beta-blockers like metoprolol, which primarily target beta-receptors.


Feature	Labetalol	Selective Beta-Blockers (e.g., Metoprolol)
Primary Mechanism	Blocks both alpha-1 and non-selective beta receptors.	Primarily blocks beta-1 receptors in the heart.
Effect on Peripheral Resistance	Reduces peripheral vascular resistance.	Can increase peripheral resistance initially.
Orthostatic Hypotension Risk	Higher risk, especially with IV form, due to alpha-1 blockade.	Lower risk compared to labetalol.
Common Side Effects	Dizziness, fatigue, nausea, scalp tingling, nasal stuffiness, sexual dysfunction.	Fatigue, dizziness, nausea, constipation, insomnia, cold extremities.
Heart Rate	Less effect on resting heart rate, maintains cardiac output.	More significant effect on slowing heart rate.
Use in Pregnancy	Considered a first-choice medication for high blood pressure during pregnancy.	Some are used, but labetalol is often preferred.

Managing Common Side Effects

For patients experiencing common, bothersome side effects, several strategies can help:

Dizziness/Lightheadedness: Move slowly when changing positions, such as rising from a chair or bed. If you feel dizzy, sit or lie down immediately until it passes.
Fatigue: Rest and get plenty of sleep. Mild fatigue often improves over time.
Nausea: Taking the medication with food can help settle the stomach. Eating smaller, more frequent meals may also be beneficial.
Tingling Scalp: This is a temporary sensation that often resolves on its own as your body adjusts to the medication.
Sexual Dysfunction: If this side effect persists and is bothersome, discuss it with your healthcare provider. They may be able to suggest alternative medications or management strategies.

Serious Side Effects to Watch For

While less common, some side effects are serious and require immediate medical attention:

Liver Injury: Symptoms can include persistent nausea, upper right abdominal pain, yellowing of the skin or eyes (jaundice), dark urine, and unexplained fatigue.
Heart Failure: Watch for shortness of breath, sudden weight gain, swelling in the ankles and feet, or an unusually slow heartbeat.
Breathing Problems: Wheezing, chest tightness, or difficulty breathing can occur, especially in individuals with a history of asthma or COPD.
Allergic Reactions: Signs include hives, rash, itching, and swelling of the face, tongue, or throat.
Severe Bradycardia: An extremely slow heart rate, potentially causing fainting.

If any of these serious symptoms occur, contact a healthcare professional immediately. Additionally, patients should never stop taking labetalol abruptly, as this can lead to serious cardiac complications.

Conclusion

For individuals on oral labetalol, dizziness is the most frequently reported side effect. However, for the IV form, orthostatic hypotension is the primary concern due to the medication's dual alpha- and beta-blocking actions. Most common side effects like dizziness, fatigue, and nausea are mild and temporary as the body adapts to the new medication. Effective management strategies, such as moving slowly to prevent dizziness and taking oral doses with food, can help mitigate these effects. Patients should be vigilant for any serious or persistent side effects and communicate openly with their healthcare provider to ensure safe and effective treatment. Always consult a doctor before making any changes to your medication regimen. For more detailed information on drug interactions and other precautions, the MedlinePlus Drug Information resource is a valuable source.

Frequently Asked Questions

Most of the common side effects, such as dizziness and fatigue, tend to be more pronounced when you first start taking the medication and generally lessen or go away completely as your body adjusts to the treatment.

Orthostatic hypotension, a form of dizziness from standing too quickly, is more common with the IV form of labetalol. While it can occur with oral tablets, it is less frequent when starting with the recommended dosage.

To manage dizziness, you should move slowly when changing positions. If you feel lightheaded, sit or lie down until the feeling passes. If the dizziness is severe or causes fainting, contact your healthcare provider.

Yes, a tingling sensation in the scalp or skin can occur, particularly during the initial phase of treatment. This is a temporary side effect that should resolve on its own.

Yes, sexual side effects like erectile dysfunction or ejaculation failure have been reported. If this is a persistent issue, speak with your healthcare provider, as they may be able to suggest other medications.

No, you should never stop taking labetalol abruptly without consulting your doctor. Suddenly stopping the medication can lead to serious heart problems, including chest pain or a heart attack. Your doctor will likely need to decrease your dose gradually.

Taking your oral dose of labetalol with food can help minimize nausea and stomach upset. Eating smaller, more easily digestible meals may also be helpful.