What is a common side effect of most mood stabilizers?

October 10, 2025 •

5 min read

According to studies, many mood-stabilizing medications can significantly impact body weight. In fact, weight gain is a common side effect of most mood stabilizers, particularly with certain classes of drugs like atypical antipsychotics and valproate.

Quick Summary

Mood stabilizers frequently cause side effects like weight gain, drowsiness, and cognitive changes. This article details the common and specific side effects associated with various mood stabilizers and provides management strategies to balance therapeutic benefits with patient tolerability.

Key Points

Weight Gain is a Common Side Effect of most mood stabilizers and is particularly associated with valproate and atypical antipsychotics, driven by increased appetite and metabolic changes.
Drowsiness and sedation are frequent, especially when first starting treatment, and may be managed by adjusting the timing of medication doses.
Gastrointestinal issues, such as nausea, vomiting, and diarrhea, are common early side effects that often improve over time or by taking the medication with food.
Cognitive difficulties, including 'brain fog,' can occur with some mood stabilizers like lithium and valproate, impacting concentration and memory.
Fine hand tremors are a common and identifiable side effect, especially with lithium and valproate.
Regular medical monitoring is crucial for certain medications, such as lithium and valproate, to check drug levels and screen for potential organ-related problems.
Lifestyle interventions, including a healthy diet and regular exercise, are important tools for mitigating side effects like weight gain.
Serious but rare side effects, like the severe rash associated with lamotrigine or organ damage with valproate, necessitate immediate medical attention if signs appear.

Mood stabilizers are a cornerstone in the treatment of mood disorders like bipolar disorder, working to regulate neurotransmitter activity and prevent extreme mood swings. However, like most medications, they can cause a range of side effects that can impact a patient's quality of life and treatment adherence. While the specific side effects vary by medication, certain issues, such as weight gain, drowsiness, and gastrointestinal distress, are commonly reported across many different types of mood stabilizers. Understanding these potential effects is crucial for both patients and healthcare providers to effectively manage treatment and maximize long-term outcomes.

The most common side effects explained

Weight gain

Weight gain is arguably the most recognized and challenging side effect associated with many mood stabilizers. Its occurrence and severity depend on the specific medication. Atypical antipsychotics, frequently used as mood stabilizers, are particularly known for their potential to cause significant weight gain and metabolic changes, including insulin resistance and elevated cholesterol. Valproate (divalproex), another common mood stabilizer, also carries a high risk of weight gain, with studies showing a notable increase in body mass in a significant portion of users.

The mechanisms behind medication-induced weight gain are complex but often involve:

Increased Appetite: Many drugs stimulate appetite, leading to higher caloric intake.
Metabolic Changes: Medications can alter how the body processes glucose and fat, promoting fat storage.
Fluid Retention: Certain drugs, notably lithium, can cause fluid retention, contributing to overall weight.

Drowsiness and sedation

Many mood stabilizers can cause drowsiness or sedation, especially when starting the medication. This can interfere with daily activities, including driving or operating machinery. For some, this effect lessens over time as the body adjusts, but for others, it may persist. Drowsiness is particularly common with atypical antipsychotics and can also occur with valproate and lithium. If sedation is bothersome, a healthcare provider might suggest adjusting the timing of the dose, for instance, taking it at bedtime.

Gastrointestinal issues

Nausea, vomiting, and diarrhea are frequent side effects, especially during the initial phases of treatment. Taking medication with food or milk can often help mitigate stomach upset. For lithium, severe or persistent vomiting and diarrhea are serious concerns that can lead to dehydration and dangerously high lithium levels.

Cognitive effects

Some patients report cognitive difficulties, often described as “brain fog,” which can include problems with concentration, memory, and mental sharpness. While the effects vary, lithium and valproate have been linked to more pronounced cognitive side effects in some individuals compared to lamotrigine. The impact can be dose-dependent, and sometimes adjustments are needed to find a balance between therapeutic effect and cognitive function.

Fine hand tremors

Fine hand tremors or shakiness are a common side effect of both lithium and valproate. While often mild, they can be bothersome and may indicate that the dose is too high. If tremors are persistent or severe, a doctor can help by adjusting the dosage or recommending a different medication.

Side effects by specific mood stabilizer

Lithium

Common: Increased thirst and urination, fatigue, fine hand tremors, weight gain, nausea.
Serious (requiring monitoring): Potential for kidney and thyroid problems, requiring regular blood tests. Dehydration can increase the risk of lithium toxicity.

Valproate (Divalproex)

Common: Significant weight gain, drowsiness, nausea, hair loss.
Serious: Rare but serious risk of liver damage and pancreatitis, requiring monitoring.

Lamotrigine

Common: Dizziness, blurred vision, headache, nausea.
Serious: Risk of a severe, life-threatening skin rash (Stevens-Johnson syndrome), especially during the first few months of treatment. Patients are advised to contact their doctor immediately at the first sign of a rash.

Atypical antipsychotics (e.g., Quetiapine, Olanzapine)

Common: Significant weight gain, drowsiness, metabolic changes (blood sugar, cholesterol), dizziness.
Serious: Risk of diabetes, high cholesterol, and involuntary movements (tardive dyskinesia) with long-term use.

Managing and coping with side effects

Managing the side effects of mood stabilizers is a collaborative process between the patient and their healthcare provider. Open communication is key to finding the right balance between therapeutic benefit and tolerability.

Dosage and Timing Adjustments: Sometimes, reducing the dose or changing the time of day the medication is taken can alleviate side effects. For example, taking a sedating medication at night can help with daytime drowsiness.
Lifestyle Interventions: For weight gain, adopting a balanced diet and incorporating regular physical activity are vital strategies. For tremors, avoiding caffeine might help.
Medication Switching or Combination: If side effects are intolerable, your doctor may suggest switching to a different medication with a more favorable side effect profile or adding another medication to help manage the side effects. Lamotrigine, for example, is often considered more weight-neutral than other mood stabilizers.
Regular Monitoring: For certain medications like lithium and valproate, regular blood tests are necessary to ensure the drug levels are safe and not causing organ damage.

Conclusion

While effective in treating mood disorders, many mood stabilizers come with potential side effects, with weight gain, drowsiness, and cognitive changes being among the most common. The experience of side effects is highly individual and depends on the specific medication, dosage, and personal factors. It's important for patients to have an open and honest dialogue with their healthcare team about any side effects they experience. By working together, patients can find an effective treatment plan that minimizes unwanted effects and supports their overall well-being. For more detailed information on specific drugs, resources like the Mayo Clinic can be valuable.

Comparison of common mood stabilizer side effects


Feature	Lithium	Valproate (Divalproex)	Lamotrigine	Atypical Antipsychotics
Primary Use	Bipolar disorder (mania/maintenance)	Bipolar disorder (mania), epilepsy	Bipolar disorder (maintenance), epilepsy	Bipolar disorder (mania/depression), schizophrenia
Weight Gain	Common, though recent meta-analysis suggests not significant for all	Common and often significant	Less common, considered weight-neutral	Common and can be significant
Drowsiness	Can occur, may lessen over time	Common, especially initially	Can occur	Common
GI Distress (Nausea)	Common, especially initially	Common, especially initially	Can occur	Can occur
Tremors	Common, fine hand tremors	Can occur	Possible, but less common	Possible (e.g., muscle stiffness)
Cognitive Effects	Possible 'brain fog'	Possible 'brain fog'	Considered to have less cognitive impact	Possible impairment
Serious Risks	Kidney/Thyroid issues, toxicity	Liver damage, pancreatitis	Severe rash (SJS/TEN)	Metabolic issues (diabetes), TD

Frequently Asked Questions

A common side effect of many mood stabilizers is weight gain, especially with medications like valproate (divalproex) and atypical antipsychotics. Other frequently reported side effects include drowsiness, nausea, and tremors.

No, not all mood stabilizers cause weight gain. While it's a prominent issue with many, particularly valproate and atypical antipsychotics, medications like lamotrigine are often considered more weight-neutral.

Yes, drowsiness and sedation are common side effects of many mood stabilizers, especially during the initial phase of treatment. This effect may lessen over time, but for persistent drowsiness, a healthcare provider might recommend taking the medication at bedtime.

Management strategies for medication-induced weight gain include maintaining a balanced diet, engaging in regular physical activity, and discussing medication adjustments with your doctor. Sometimes, changing to a different, more weight-neutral medication may be an option.

Common side effects of lithium include increased thirst and urination, fine hand tremors, fatigue, and nausea. Regular blood tests are necessary to monitor lithium levels to prevent toxicity.

If you experience any severe or unbearable side effects, you should contact your doctor immediately. Examples of severe reactions include a sudden rash (with lamotrigine), signs of organ damage (with valproate), or symptoms of lithium toxicity.

No, blood tests are not necessary for all mood stabilizers. However, they are essential for medications like lithium and valproate to check drug levels and monitor organ function, such as the kidneys and liver.