Hello, With reference to your query regarding whether you can take 2x20 mg testosterone or 1x40 mg administered concurrently. Testosterone is a hormone produced primary in the testicles. It helps to maintain men's bone density, fat distribution, muscle strength and mass, red blood cell production, sex drive, sperm production. It peaks during adolescence and early adulthood and as you get older, your testosterone level gradually declines. Dosage depends on what for you are taking testosterone injection. Is it to treat sexual dysfunction and growth related issues in men? It improve male libido and used extensively to treat erectile dysfunctions and also to strengthen erections. Also helps men with respect to sperm count who have a problem of with infertility. It also energizes you and gives you strengths to perform various heavy tasks. Oral dosage is not as effective as intramuscular. It mixes in the blood immediately to show instant results. The dosage depends on the age and stimulation of the individual. For bodybuilding 1-2 mgs/week can be given and for infertility and erectile dysfunction varies from 400-800 mg/week. Hence, I am not sure for what purpose you have been advised to take testosterone injection. It would be best to consult your physician for further details. Thank you.