A 2016 phase 1–2 prospective study orally administered 800 mg per day to 27 patients with telomere diseases. The primary efficacy endpoint was a 20% reduction in the annual rate of telomere attrition measured. Toxic effects formed the primary safety endpoint. The study was halted early, after telomere attrition was reduced in all 12 patients who could be evaluated. 12 of 27 patients achieved the primary efficacy end point, 11 of whom increased telomere length at 24 months. Hematologic responses (secondary efficacy endpoint) occurred in 10 of 12 patients who could be evaluated at 24 months. Elevated liver-enzyme levels and muscle cramps (known adverse effects) of grade 2 or less occurred in 41% and 33% of the patients, respectively. 
The common side effects of oxymetholone include depression , lethargy , headache , swelling , rapid weight gain , priapism , changes in skin color, urination problems, nausea , vomiting , stomach pain (if taken on an empty stomach), loss of appetite , jaundice , breast swelling in men, feeling restless or excited, insomnia , and diarrhea .  In women, side effects also include acne , changes in menstrual periods , voice deepening , hair growth on the chin or chest , pattern hair loss , enlarged clitoris , and changes in sex drive .   Because of its 17α-alkylated structure, oxymetholone is hepatotoxic .  Long term use of the drug can cause a variety of serious ailments, including hepatitis , liver cancer , and cirrhosis ; therefore periodic liver function tests are recommended for those taking oxymetholone.