When you’re managing bipolar disorder with lithium carbonate, it’s not just about taking a pill every day. The difference between stability and crisis often comes down to a tiny number on a lab report: your serum lithium level. And if you’re on a generic version - which most people are - that number can shift unexpectedly, even if the dose hasn’t changed.
Why Generic Lithium Isn’t Always Interchangeable
Lithium carbonate is one of the oldest psychiatric medications still in widespread use. It’s been around since the 1940s, and it works. But it’s also one of the most dangerous if not monitored closely. Its therapeutic window is razor-thin: 0.6 to 1.2 mmol/L. Go below that, and mood episodes return. Go above 1.5 mmol/L, and you risk seizures, kidney damage, or even cardiac arrest. Most patients now take generic lithium carbonate instead of branded versions like Camcolit or Priadel. That’s fine - generics are cheaper and FDA-approved to be bioequivalent. But bioequivalence doesn’t mean identical. The FDA allows generics to vary by up to 20% in how much drug enters your bloodstream compared to the brand. For most medications, that’s acceptable. For lithium? It’s risky. A 2024 study in the Journal of Psychopharmacology found that patients switched from one sustained-release generic to another - even with the same milligram dose - showed an 11% average increase in serum lithium levels. Four patients in that study crossed into toxic range (above 1.3 mmol/L) after a simple brand switch. One reached 1.88 mmol/L - nearly double the upper safety limit. Why? Because release rates differ. Immediate-release lithium hits your blood in 1-2 hours. Sustained-release versions like Priadel or Camcolit take 4-5 hours. Even small differences in coating, particle size, or manufacturing can change how fast lithium dissolves in your gut. And since lithium is cleared by your kidneys, any spike in blood concentration puts extra strain on them.Therapeutic Targets: What Level Should You Be At?
There’s no single “right” level for everyone. It depends on your age, your formulation, and whether you’re in an acute episode or maintaining stability.- Acute mania or depression: Target 0.8-1.0 mmol/L. Studies show this range cuts relapse risk by more than half compared to lower levels.
- Maintenance therapy: 0.6-0.8 mmol/L is now widely recommended, especially for older adults or those with kidney issues.
- Sustained-release formulations: Aim for the upper end of the range - 0.8-1.0 mmol/L. These release lithium slowly, so your peak levels are lower, but your overall exposure is similar.
- Patients over 60: Many experts recommend lowering targets by 20-25%. Kidney function declines with age, and lithium clearance drops. A level of 0.7 mmol/L in a 70-year-old might be equivalent to 0.9 mmol/L in a 30-year-old.
When and How to Check Your Levels
Timing matters as much as the number itself. If you’re on a standard-release lithium tablet taken three times a day, your blood should be drawn 12 hours after your last dose - usually just before your morning pill. That’s when your level is most stable and reflects your average exposure. But if you’re on once-daily sustained-release lithium (like Priadel or a generic equivalent), you draw blood 24 hours after your last dose. Why? Because the drug is still being released slowly into your system. Drawing too soon gives you a falsely low reading. Don’t assume your level is stable just because you’ve been on the same dose for months. Lithium levels can drift due to:- Changes in salt intake (low sodium = higher lithium levels)
- Dehydration (even mild, from fever or hot weather)
- Starting or stopping diuretics, NSAIDs, or ACE inhibitors
- Changes in kidney function
- Switching between generic brands
What Else Needs Monitoring
Lithium doesn’t just affect your brain. It affects your kidneys, thyroid, and electrolytes.- Thyroid: 5-15% of long-term users develop hypothyroidism. Get a TSH test every 6-12 months. If your TSH rises above 4.5 mIU/L, you may need levothyroxine.
- Kidneys: Lithium can cause chronic kidney disease over time. Monitor serum creatinine and calculate eGFR. The 2022 CANMAT guidelines now recommend using cystatin C instead of creatinine alone - it’s more accurate in older adults and those with low muscle mass.
- Electrolytes: Sodium and potassium imbalances can push lithium levels dangerously high. Avoid low-sodium diets unless medically necessary.
- Heart: Lithium can worsen Brugada syndrome or cause arrhythmias in people with pre-existing heart conditions. Avoid if you have this condition.
Who Shouldn’t Take Lithium
Lithium isn’t for everyone. Absolute contraindications include:- Severe kidney disease (eGFR below 30 mL/min)
- Brugada syndrome
- Severe cardiovascular disease
- Pregnancy (especially first trimester - lithium carries a small risk of Ebstein’s anomaly)
- Dehydration or severe illness
Why Brand Switching Can Be Dangerous
Pharmacists are trained to substitute generics to save money. But with lithium, that’s not always safe. A 2023 FDA draft guidance specifically warns that modified-release lithium products are “pharmacokinetically complex” and require special testing to prove equivalence. Yet many generic manufacturers don’t provide detailed release profiles. Some pharmacies don’t even know which version they’re dispensing. In the UK and US, about 12.5% of lithium prescriptions are written without specifying brand. That means you could get Camcolit one month, a no-name generic the next, and Priadel the month after. All labeled “lithium carbonate 600 mg.” But they’re not the same. If you’ve been stable on one brand, ask your doctor to write “Dispense as written” or “Do not substitute” on your prescription. If your pharmacy switches your medication, ask for a serum level check within 7-10 days.What’s Next for Lithium Therapy
Lithium isn’t going away. Despite newer drugs like lamotrigine and cariprazine, it’s still the most effective at preventing suicide in bipolar disorder. The 1981 study by Baastrup and Schou showed it cuts suicide risk by over 80% - a benefit no other mood stabilizer has matched. Research is moving toward personalization. The International Consortium on Lithium Genetics (ConLiGen) has identified 30 genetic variants linked to how people process lithium. Some people naturally clear it faster. Others hold onto it longer. Early AI tools are being tested in academic centers. They use your age, weight, kidney function, genetics, and even your diet to predict the right dose - before you even start. But for now, the gold standard is still: test your blood, track your levels, and never assume two generics are the same.What You Can Do Right Now
If you’re on lithium carbonate:- Know your last serum level - write it down.
- Know which formulation you’re on - immediate-release or sustained-release?
- Ask your pharmacist: Is this the same brand I’ve been taking?
- Check your blood 7-10 days after any switch.
- Get thyroid and kidney tests every 6 months - don’t wait for symptoms.
- Drink water consistently. Avoid crash diets or extreme salt restriction.
- Tell every new doctor you see: I’m on lithium.
