Most doses of Eli Lilly's diabetes drug Mounjaro and weight-loss drug Zepbound would be in limited supply through the second quarter of this year due to increased demand, the U.S. Food and Drug Administration's website showed on Wednesday.

Both drugs had limited availability for the 5 milligram (mg), 7.5 mg, 10 mg, 12.5 mg and 15 mg doses, the website noted. The 2.5 milligram doses for the treatments were listed as available.

Previously, some doses of both the drugs were expected to be available in limited quantities through April. Doses of Mounjaro have been available in limited amounts since February.

The 1.5 mg and 4.5 mg doses of Trulicity, another diabetes drug by Lilly, will also be available in limited amounts through April due to increased demand, according to the FDA's website.

Increasing demand for a type of highly effective diabetes and weight-loss treatment known as GLP-1 agonists has led to supply constraints for drugmakers such as Lilly and Novo Nordisk. 

"While we anticipate limited availability in the near term, we expect our investments in manufacturing and supply capacity to progressively increase production of our medicines throughout 2024 and beyond," a spokesperson for Lilly said.

The drugmaker has also advised patients to plan ahead for refills of their medicines by contacting their pharmacy at least one week before the refill is needed.

Mounjaro has been approved since 2022 for patients with Type-2 diabetes to control their blood sugar levels. It was approved in the U.S. for weight loss under the brand name Zepbound late last year.

Separately, Lilly said earlier on Wednesday that tirzepatide - the active ingredient in both Mounjaro and Zepbound - helped ease symptoms of a common sleep-related breathing disorder across two late-stage studies.