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. 
Heavy consumption of the essential amino acid lysine (as indicated in the treatment of cold sores) has allegedly shown false positives in some and was cited by American shotputter C. J. Hunter as the reason for his positive test, though in 2004 he admitted to a federal grand jury that he had injected nandrolone.  A possible cause of incorrect urine test results is the presence of metabolites from other AAS, though modern urinalysis can usually determine the exact AAS used by analyzing the ratio of the two remaining nandrolone metabolites. As a result of the numerous overturned verdicts, the testing procedure was reviewed by UK Sport . On October 5, 2007, three-time Olympic gold medalist for track and field Marion Jones admitted to use of the drug, and was sentenced to six months in jail for lying to a federal grand jury in 2000. 
There are also some who complain of joint pain when using Winstrol. As a steroid that does not aromatize there will be no water retention but the “dry feeling” may not be what many think it is. Most who use the steroid will be physique athletes or gym rats during a cutting phase. They will also typically add it into a plan late in the diet once they’re already lean. Typically, when you become very lean, bodybuilding lean, this makes the joints a little uncomfortable. With or without Winstrol this discomfort could potentially exist. As for pro athletes who have nearly every last steroid at their disposal, remember, if Winstrol weren’t effective in competitive sports so many athletes wouldn’t make it a primary and favorite choice. In fact, the combo of Winstrol with low doses of Nandrolone is a very common stack among many athletes, and this stack will greatly eliminate any potential joint discomfort should it exist.