How to tell if your lithium level is too high? Signs and Symptoms of Toxicity

October 14, 2025 •

4 min read

Since lithium has a narrow therapeutic range, it doesn't take much for levels to become toxic. This makes understanding how to tell if your lithium level is too high? critical for anyone taking this mood stabilizer for conditions like bipolar disorder.

Quick Summary

Recognizing the signs of lithium toxicity, which range from mild gastrointestinal upset to severe neurological issues, is crucial for patient safety. This guide details symptoms, risk factors, and necessary steps to take if an overdose is suspected.

Key Points

Early Signs: Mild toxicity often starts with gastrointestinal issues like nausea, vomiting, and diarrhea, along with a fine hand tremor.
Advanced Neurological Symptoms: As levels rise, neurological symptoms such as confusion, slurred speech, poor coordination (ataxia), and blurred vision will appear.
Life-threatening Risks: Severe toxicity can lead to seizures, irregular heart rhythms, kidney failure, and coma, necessitating emergency treatment.
Blood Test Is Definitive: The only way to confirm toxicity is with a serum lithium blood test, which measures the concentration in your blood.
Hydration and Diet Matter: Dehydration and changes in sodium intake can significantly increase lithium levels and the risk of toxicity.
Drug Interactions: Taking NSAIDs, certain diuretics, or ACE inhibitors can raise lithium levels. Always inform your doctor and pharmacist of all medications you take.
Seek Immediate Help: If you suspect lithium toxicity, stop taking the medication and seek emergency medical assistance immediately.

Understanding Lithium's Narrow Therapeutic Range

Lithium is a medication widely used to treat mood disorders, particularly bipolar disorder. It is a highly effective mood stabilizer, but it is also known as a narrow therapeutic index drug. This means there is a very small difference between an effective dose and a toxic one. Even minor fluctuations in blood concentration can lead to serious health problems, including potentially life-threatening complications.

Because of this, anyone taking lithium must be vigilant for signs of toxicity and undergo regular blood tests to monitor their serum lithium levels. The body's ability to excrete lithium can be affected by many factors, including hydration levels, sodium intake, and kidney function, all of which can increase the risk of toxicity.

Signs and Symptoms of Lithium Toxicity

Symptoms of lithium toxicity typically progress in severity as the concentration of lithium in the blood rises. It is important to remember that some mild symptoms can overlap with common side effects, but any worsening of symptoms or the appearance of new ones should be addressed immediately.

Mild Toxicity (Lithium Level 1.5–2.5 mEq/L)

At this level, symptoms may be subtle but should not be ignored. Contacting a healthcare provider is essential.

Gastrointestinal: Nausea, vomiting, diarrhea, and stomach pain.
Neurological: Fatigue, lethargy, and a mild, fine tremor in the hands.
General: Increased thirst (polydipsia) and frequent urination (polyuria).

Moderate Toxicity (Lithium Level 2.5–3.5 mEq/L)

At this stage, symptoms become more pronounced and demand urgent medical attention.

Neurological: Confusion, agitation, slurred speech (dysarthria), and a coarse, more pronounced tremor.
Coordination: Problems with balance and coordination (ataxia), dizziness, and muscle twitches (myoclonus).
Vision: Blurred or double vision.
Cardiovascular: Rapid or irregular heartbeat (tachycardia).

Severe Toxicity (Lithium Level > 3.5 mEq/L)

This is a medical emergency and can lead to permanent neurological damage, coma, or death if not treated immediately.

Neurological: Seizures, hyperthermia (severely elevated body temperature), and changes in consciousness ranging from delirium to coma.
Renal: Acute kidney failure.
Cardiovascular: Dangerous heart rhythm abnormalities.

Differentiating Mild Side Effects from Toxicity

Because some of the early signs of toxicity can mimic common, less severe side effects, it is crucial to recognize the distinction. Worsening severity, the appearance of new symptoms, or multiple symptoms simultaneously are red flags for toxicity.


Symptom	Common Side Effect	Sign of Toxicity	Action Required
Hand Tremor	Mild, fine tremor when starting medication or after dose change.	Worsening, coarse, and uncontrollable tremor.	Contact healthcare provider for blood level check.
Nausea/Vomiting	Mild upset stomach, often subsiding after a few weeks.	Persistent, severe, or new-onset nausea and vomiting.	Immediate medical attention.
Drowsiness/Fatigue	General tiredness, especially when starting the medication.	Significant lethargy, confusion, or difficulty staying awake.	Immediate medical attention.
Increased Urination/Thirst	Can occur early in treatment.	Excessive, uncontrolled urination and thirst (signs of nephrogenic diabetes insipidus).	Seek urgent medical advice.
Blurred Vision	Not a common side effect.	A clear indicator of moderate to severe toxicity.	Immediate medical attention.

Risk Factors That Increase Lithium Levels

Several factors can disrupt the delicate balance of lithium in the body. Being aware of these can help prevent a toxic build-up:

Dehydration: Caused by fever, excessive exercise, vomiting, or diarrhea.
Low Sodium Intake: Sudden changes to a low-salt diet can increase lithium reabsorption in the kidneys, leading to higher blood levels.
Reduced Kidney Function: As lithium is excreted through the kidneys, impaired renal function can cause it to accumulate.
Interacting Medications: Some drugs can significantly raise lithium levels, including nonsteroidal anti-inflammatory drugs (NSAIDs), certain diuretics (water pills), and ACE inhibitors.
Age: Older adults may be at a higher risk due to natural changes in kidney function.

What to Do If You Suspect High Lithium Levels

If you or someone you know shows signs of potential lithium toxicity, it is a serious medical situation. Do not wait for symptoms to worsen.

Immediate Action Required:

Stop taking lithium and any interacting medications immediately.
Contact your local emergency services (e.g., 911) or a poison control center immediately.
Go to the nearest emergency department. Bring the lithium container with you if possible.
Inform the medical staff that lithium toxicity is suspected.

The Role of Blood Monitoring

Regular blood tests are the most important tool for monitoring lithium therapy and preventing toxicity. Your healthcare provider will establish a therapeutic range and check your levels periodically, especially after a dosage change or if you report new symptoms. For accurate results, blood should be drawn 10-12 hours after your last dose.

Conclusion

Recognizing the warning signs of elevated lithium levels is essential for patient safety. From mild side effects like nausea and tremors to severe neurological complications, symptoms progress with increased concentration. Knowing the risk factors, such as dehydration or drug interactions, and taking proactive steps like consistent blood monitoring are key to preventing a toxic buildup. If toxicity is suspected, immediate medical attention is non-negotiable. For a comprehensive overview of lithium toxicity, consult the information from the Cleveland Clinic.

Frequently Asked Questions

A therapeutic serum lithium level is generally between 0.6 and 1.2 mEq/L. Levels above 1.5 mEq/L are considered toxic and require medical evaluation.

A common side effect is a mild, fine hand tremor that may decrease over time. A tremor that becomes coarse, uncontrolled, or worsens noticeably, especially alongside other symptoms like confusion or slurred speech, is a strong indicator of toxicity.

No, not always. While a high blood level increases the risk, lithium toxicity can occur even with blood levels within the normal range, particularly in older adults or those with underlying health conditions like kidney disease.

Common causes include dehydration (from fever, sweating, or inadequate fluid intake), significant changes in sodium intake (like starting a low-salt diet), reduced kidney function, or drug interactions with medications like NSAIDs or diuretics.

Acute toxicity results from taking a large dose at once and typically involves significant gastrointestinal symptoms followed by neurological ones. Chronic toxicity occurs when lithium slowly builds up over time and mainly features neurological symptoms and potential kidney damage.

Yes, if you suspect lithium toxicity based on your symptoms, you should stop taking the medication and seek immediate medical attention. Do not adjust your dose or resume taking it without a doctor's guidance.

Inform them immediately that you take lithium and suspect toxicity. Provide your recent medication list, including any changes, and describe your symptoms and when they began. Bring the lithium container with you to the hospital.

Untreated severe or chronic lithium toxicity can lead to permanent neurological damage, long-term memory and mood problems, kidney disease, movement disorders, and in rare cases, death.

Yes, avoid nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, certain diuretics like hydrochlorothiazide, and ACE inhibitors unless specifically approved by your doctor, as they can significantly raise lithium levels.