Patients who are prescribed Adderall could have trouble filling their prescriptions.

That's because pharmaceutical companies are facing supply chain disruptions, Bloomberg reported.

This has led to pharmacies nationwide, including Walmart, CVS, and Walgreens, having difficulty keeping the ADHD medication in stock at locations nationwide.

A pharmacist at Walmart told EW Scripps that another issue with the shortage is that only a few drugmakers provide the medication.

According to the American Society of Health-System Pharmacists (ASHP), which tracks current drug shortages, pharmaceutical companies Par and Teva estimate a release date for their 20 mg capsules by early September.

ASHP's website said Sandoz estimates a release date of its 20 mg capsules sometime this month.

Teva could see 25 mg and 30 mg capsules being available in mid-September, the ASHP website said.

According to ASPH, companies Rhodes, Sandoz, and Amneal have several different Adderall milligrams available.

Companies like Shire, Prasco, and Lannett say they have products available, ASHP said.