Can one take B vitamin tablets (like B6+B12) daily a dose without the doctor's prescription without any harm to oneself?

Hi Qudsia Sultana, Was there a specific health issue or condition that your friend was recommending the Vitamin B for?

Generally, one can take Vitamin B tablets safely as long as you don't exceed the recommended daily allowance. For example, RDA for B12 is the 2.4 micrograms per day for adults and adolescents aged 14 years and older, 2.6 micrograms per day for adult and adolescent pregnant females, and 2.8 micrograms per day for adult and adolescent lactating females, says the National Institutes of Health.

Here's what they had to say about Vitamin B6.

Recommended Dietary Allowances (RDAs) of vitamin B6: Males (19-50 years) 1.3 milligrams; males (51 years and older) 1.7 milligrams; females (19-50 years) 1.3 milligrams; females (51 years and older) 1.5 milligrams. Some researchers think the RDA for women 19-50 years should be increased to 1.5-1.7 milligrams per day. Pregnant women, 1.9 milligrams; and lactating women, 2 milligrams.

Recommended maximum daily intake of vitamin B6: Adults, pregnant, and lactating women (over 18 years) 100 milligrams. A doctor and pharmacist should be consulted for dosing in other conditions.

Certain medications or even allergies to substances such as cobalt could cause some issues, however.

For more information on B6, see this link ...
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-b6.html

For more info on B12, check out this link
http://www.nlm.nih.gov/medlineplus/ency/article/002403.htm

If you are using any of those medications or experience the allergies mentioned, you'll want to check with your doctor.
Does that help answer your questions?