What causes high red blood count on blood tests? Can it be caused by medications?Can it be caused by

Dehydration

"A high red blood cell count may be a symptom of a disease or disorder. But, it doesn’t always mean that you have a health problem. Health or lifestyle factors can also cause a high red blood cell count.

Medical conditions that can cause an increase in red blood cells include:

Heart failure, causing low blood oxygen levels.
Congenital heart disease (“congenital” means you’re born with it).
Polycythemia vera (a rare blood cancer in which your bone marrow produces too many red blood cells).
Kidney tumors.
Lung disease, such as emphysema, COPD, pulmonary fibrosis (scarring of your lung tissue).
Hypoxia (low blood oxygen levels).
Carbon monoxide exposure (usually related to smoking).
Sleep apnea.
Lifestyle factors that can cause a high red blood cell count include:

Smoking cigarettes.
Living at a high altitude.
Taking performance-enhancing drugs such as anabolic steroids (for example, synthetic testosterone) or erythropoietin.
What cancers cause high red blood cell count?
Many cancers actually cause your red blood cells to drop. However, there are some cancers that can result in a high red blood cell count, including:

Polycythemia vera (a rare blood cancer that causes your body to make too many red blood cells).
Renal cell carcinoma (the most common type of kidney cancer among adults).
Hepatocellular carcinoma (the most common type of liver cancer among adults).
Can stress cause a high red blood cell count?
Yes. Research has shown a link between stress and its effect on your blood cells. Stress can lead to an increase in red blood cells, neutrophils (a type of white blood cell) and platelets."

Source: Cleveland Clinic

I advice you to discuss the result of your blood work with your Dr..