Viagra is available in doses of 25, 50 and 100 milligrams (mg). Consult with a doctor, who can recommend which dose is right for you.

If you are prescribed either the 25mg or 50mg doses, you may elect to buy Viagra at the next-highest dosage amount and use a pill splitter that will cut the pills in half, thereby acquiring the desired dosage. Because Viagra pills are similar in price regardless of the dosage amount, many patients find they can save a substantial amount of money by pill splitting. 

If you do not get the results that you expect after taking an ED pill on more than two occasions, talk to your doctor.