Lithium and salt in your diet

This is educational information, not medical advice. It’s also the interaction nobody warns you about at the pharmacy counter, because it isn’t a medicine. It’s dinner.

Cutting salt tends to push lithium levels up. Adding salt tends to pull them down. Both directions are worth saying out loud, because the useful conclusion comes from having both.

Why your kidneys mix them up

Lithium and sodium look fairly similar to a kidney. Similar enough that the kidney doesn’t reliably tell them apart, and treats lithium a bit like it treats salt.

So it behaves like a doorman who can’t tell twins apart. When salt is scarce, the instruction is hold on to sodium — and lithium gets held on to as well, because it walks in wearing the same face. Less leaves your body. The level in your blood goes up.

When salt is plentiful, the opposite. The kidney lets sodium go, and lets more lithium go with it. The level comes down.

Why “eat less salt” is the wrong takeaway, and so is “eat more”

Here’s the part that actually protects you: your lithium level was measured against the way you normally eat.

That number on your last blood test isn’t a property of the tablet. It’s a snapshot of you, on your usual diet, at your usual dose. Change the diet substantially and you’ve moved the number, in one direction or the other, without anyone deciding to.

So the instruction isn’t more salt or less salt. It’s roughly the same amount, most days. Consistency is doing the work here, not a target.

Where the change sneaks in

Almost never as a decision about salt. Usually as something else entirely:

• New blood-pressure advice, and a low-sodium diet arriving with it.
• A big shift in how you eat: cutting out processed food, cooking from scratch after years of not, a new eating plan, a crash diet.
• Fasting, religious or otherwise.
• Heavy sweating over days rather than hours, which costs salt as well as fluid. More on that in lithium in hot weather.
• Illness with vomiting or diarrhoea, which strips both at once.
• Water tablets and some blood-pressure medicines, which change how your kidneys handle sodium directly.

Notice how few of those feel like a medication decision. That’s the whole problem.

What people are commonly told

The general pattern is to keep salt and fluid intake reasonably steady, and to treat any planned change as worth a mention rather than a secret. Prescribers often want to know before a diet changes, because the sensible response is usually to watch a level rather than to forbid anything.

That’s a pattern, not a prescription for you. And nobody should be salting their food to manage a blood level. That’s a job for a test and a clinician.

Signs that need attention now

If a level climbs too far, the body tends to announce it. Watch for a coarse tremor that’s new or noticeably worse, nausea, vomiting or diarrhoea, unsteadiness on your feet, slurred speech, or confusion or unusual drowsiness.

Lithium toxicity is treated as a medical emergency. Contact your prescriber or emergency services the same day rather than waiting it out. A sudden low-salt diet is one of the situations that makes this more likely, which is why the threshold should be low in the weeks after a change.

The other direction is quieter and slower. A level that has drifted too low doesn’t announce itself with symptoms; it shows up later as the mood protection thinning out. That’s not an emergency, but it is a reason to mention a diet change rather than assume it doesn’t count.

The question to bring

One line for your Medication Map: My diet is about to change in this way. Do you want to check a level? Ask it before, not after, and it stops being a problem.

The rule that doesn’t change

Never stop, start or adjust lithium yourself because of something you read here, and don’t use salt to try to steer your levels in either direction. If you think your level may be off, that’s a call to your care team.

Common questions

Does eating less salt raise lithium levels?

Yes, that's the usual direction. When sodium is scarce, your kidneys hold on to more of it — and hold on to more lithium at the same time, because they handle the two similarly. Less lithium leaves, so blood levels tend to rise.

Does eating more salt lower lithium levels?

Generally yes. More sodium going through the kidneys means more lithium goes out with it, and levels tend to fall. That isn't a bonus: a level that drops too far means less protection against episodes.

Should I eat more salt, then?

No. The point isn't a direction to move in, it's steadiness. Your blood level was measured against your ordinary diet, so changing that diet moves the level either way. If your diet is about to change for any reason, tell your prescriber before rather than after.

What if I'm told to cut salt for my blood pressure?

That's a real and common situation, and it's exactly the moment the two prescribers need to know about each other. Don't drop the salt advice and don't quietly ignore it. Say that you take lithium, and let them sort out the monitoring between them.

Read next

• Bipolar Meds: Build a Toolkit (Not a Magic Pill)
• Bipolar medication: a calm, plain-language guide
• Lithium for bipolar disorder: what to expect
• Lithium in hot weather: what changes
• Can you drink alcohol on lithium?

Sources

• MedlinePlus — Lithium
• Goodwin & Jamison — Manic-Depressive Illness (2nd ed., chs. 17 and 20)
• Miklowitz — The Bipolar Disorder Survival Guide, 3rd ed. (ch. 6)
• NIMH — Bipolar Disorder
• DBSA — Medications

If you’re in crisis or thinking about harming yourself, you’re not alone and help is available right now. In the US & Canada call or text 988. In the UK & Ireland call 116 123 (Samaritans). Elsewhere, contact your local emergency services — Get Help Now lists lines by country.