Lithium: Serum Level Monitoring, Sodium and Fluid Balance, and Toxicity Signs

Who needs this teaching

Clients who take lithium for bipolar disorder, and the family. Lithium is a mood stabilizer with a narrow therapeutic range. The kidneys excrete lithium together with sodium. Sodium loss or dehydration increases renal lithium reabsorption and causes toxicity. Older adults and clients with renal impairment have a higher risk of toxicity.

The priority teaching points

1. Serum lithium levels. The therapeutic maintenance level is usually 0.6 to 1.2 mEq/L, or the target the provider sets. Draw the trough level 12 hours after the last dose. On test days, take the morning dose after the blood draw. Levels are checked frequently at the start and after each dose change, then every 3 to 6 months. Toxicity begins above 1.5 mEq/L.
2. Kidney and thyroid monitoring. Lithium causes hypothyroidism and impairs renal concentrating ability (nephrogenic diabetes insipidus). Check serum creatinine, TSH, and calcium before treatment, then every 6 to 12 months or as ordered. Report fatigue, cold intolerance, and weight gain.
3. Sodium and fluids. Keep dietary sodium normal and consistent. Do not start a low-sodium diet without the provider. Drink 2 to 3 L of fluid daily unless a restriction is prescribed. Increase fluids during hot weather, heavy exercise, and fever. Report vomiting or diarrhea, because both cause sodium and fluid loss.
4. Expected effects. Fine hand tremor, thirst, polyuria, mild nausea, and weight gain are common. Take lithium with food at the same times each day. A coarse or worsening tremor indicates toxicity.
5. Interactions. NSAIDs (ibuprofen, naproxen), thiazide diuretics, ACE inhibitors, and angiotensin II receptor blockers raise serum lithium levels. Avoid nonprescription NSAIDs. Ask the provider before any new prescription; the provider checks the lithium level after a change. Keep caffeine intake consistent.
6. Toxicity response. Early toxicity signs are diarrhea, vomiting, coarse tremor, drowsiness, and muscle weakness. Hold the dose and call the provider the same day. Severe toxicity signs are confusion, ataxia, slurred speech, muscle twitching, seizures, and a decreased level of consciousness. Call 911.
7. Pregnancy planning. First-trimester lithium exposure increases the risk of fetal cardiac malformations, including Ebstein anomaly. Clients who can become pregnant discuss contraception and pregnancy planning with the provider before conception. Do not stop lithium abruptly; abrupt discontinuation increases the risk of relapse.

Red flags the client reports

Teach-back questions

• "When will you have your lithium level drawn?"
• "How much fluid will you drink each day?"
• "What will you do on a hot day or when you have diarrhea?"
• "Which pain relievers will you avoid?"
• "Which signs mean you hold your dose and call?"

Teaching tips

• Write the target level, the next blood draw, and the 12-hour timing on the handout.
• Include the family, because confusion is a sign of severe toxicity.
• Review every prescription and nonprescription drug for NSAIDs and diuretics.
• Use a water bottle with volume marks to track daily fluid intake.

Read more on NCLEXPace

• Therapeutic Drug Levels: The Four You Must Know
• Psychiatric Medications: The Four Emergencies
• Electrolyte Imbalances: One Table for All of Them

Sources

• Lithium Carbonate Capsules and Tablets: FDA prescribing information, including boxed warning (DailyMed).
• Yatham LN, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) and International Society for Bipolar Disorders (ISBD) 2018 Guidelines for the Management of Patients With Bipolar Disorder. Bipolar Disord. 2018;20(2):97-170.