The Link Between Lithium and Weight Gain

Explore the mechanisms by which lithium may increase your scale number.

Close-up of woman's feet on scale
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There is no question that lithium used to treat bipolar disorder can potentially cause weight gain. This is supported by studies showing that people who take lithium are prone to adding weight, mostly if they're taking it long-term.

But it's not entirely clear why weight gain occurs. Researchers believe that lithium may impact your hunger levels or the hormones your body uses to store fat and control blood sugar, leading to weight gain and other undesirable effects, such as high cholesterol.

What Is the Link Between Lithium and Weight Gain?

Weight gain was noted as a side effect almost immediately when psychiatrists started using lithium to treat bipolar disorder. In fact, according to an early drug study using lithium, about 20 percent of patients experienced weight gain of over 20 pounds. 

In a large 2012 meta-analysis of fifty-five studies in Lancet, people who received lithium had significantly more weight gain than those who received placebo. 

Of course, not everyone gains weight while on lithium. When people do gain weight, though, they gain approximately 13 to 14 pounds, and the majority of this weight gain seems to occur within the first two years of treatment.

In addition, scientists believe that weight gain from lithium is dose-dependent, meaning the higher the dose, the more likely a person is to gain weight. Also, people who are overweight before starting lithium treatment may be more likely to gain weight from the medication.

However, it is important to remember that lithium is far from alone when it comes to weight gain from bipolar disorder medications. Depakote (valproate), Clozaril (clozapine) and Zyprexa (olanzapine) also can cause significant weight gain, as can other bipolar disorder medications. 

Why Do People Gain Weight From Lithium?

It is not entirely clear why some people gain weight with chronic lithium intake, although there are several theories.

One theory involves the chemical serotonin which regulates many functions in the body including appetite. Lithium changes how your body produces and uses serotonin, which may lead to an increased appetite (and the resulting weight gain). However, one study that looked at hunger in people without bipolar who took lithium found no major impact on hunger.

Lithium also causes increased thirst, and another unproven theory is that this thirst leads people to consume high-calorie fluids such as sugary sodas and juices, leading to weight gain.

It's also possible that lithium changes the levels of your fat storage-regulating hormones directly, leading your body to store more calories as fat. The drug may also cause your metabolism to slow down, which means you'll burn fewer calories in general (and again, store more as fat).

Lithium may also cause some people to retain more sodium which can lead to swelling and weight gain. An increase in steroid hormone levels in the body can also cause weight gain, another proposed mechanism of lithium-induced weight gain.

A Word From Verywell

Weight gain is certainly an undesirable side effect of lithium treatment. However, there are several common sense steps you can take to minimize and perhaps even avoid this particular side effect:

  • Watch your consumption of high-calorie beverages, including sodas, juices, and sugary coffee drinks. When you get thirsty, choose water or something that doesn't contain calories.
  • Start and devise a regular exercise program under the guidance of your doctor.
  • Monitor your weight. If it starts to creep up, talk to your doctor about additional steps you can take to avoid further weight gain (and hopefully lose the weight you've already gained). 

While there are currently no specific medications used to treat weight gain from lithium, one 2016 case report in Clinical Psychopharmacology Neuroscience suggests that metformin may lead to weight reduction after a person gains weight from lithium.

Of course, this is a study on one person, so larger trials need to be done. Nevertheless, it is a thought-provoking first step. 


Hasnain M, Vieweg Wv. Weight considerations in psychotropic drug prescribing and switchingPostgrad Med. 2013 Sep;125(5):117-29.

McKnight RF, Adida M, Budge K, Stockton S, Goodwin GM, Geddes JR. Lithium toxicity profile: a systematic review and meta-analysis. Lancet. 2012 Feb 25;379(9817):721-8.

Praharaj SK. Metformin for lithium-induced weight gain: A case report. Clin Psychopharmacol Neurosci. 2016 Feb;14(1):101-3.

Shrivastava A et al. Weight-Gain in Psychiatric Treatment: Risks, Implications, and Strategies for Prevention and ManagementMens Sana Monographs. 2010 Jan;8(1):53-68.

Torrent C et al. Weight gain in bipolar disorder: pharmacological treatment as a contributing factor. Acta Psychiatr Scand. 2008 Jul;118(1):4-18. 

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