Yes, it would be a good idea to be taking some vitamins
For starters, a good quality multiple vitamin and mineral supplement is a must. Look for a type that's "super" or "forte" as these will have extra B-vitamins. Quest, Jamieson or Swiss Naturals are good brands to look for in Canada, there are others.
Next, a calcium-magnesium supplement is in order. Calcium isn't just for old ladies
.. it's a vital mineral for all adults, and magnesium is essential for the proper balance and function of other minerals in the body. Calcium requirement is 800 - 1000mg per day for adults, magnesium 450mg. You can buy cal-mag together as one pill, generally 2:1, or 333mg cal to 167mg mag. Take 3 a day ... take the last one in the evening, it's known to be helpful for sleep.
Lastly, potassium. You can take as a pill, 90 to 100mg is the usual amount found per tablet. Normally, it's recommended that low carbers take 400 - 500mg per day at the beginning of the program, to replace potassium that's washed out with the increased amounts of urine a person experiences with ketosis. I'm assuming you're past that point now ... a maintenance dose of at least 100mg a day is a good idea. You can also use a salt substitute, such as No Salt, Nu Salt or HalfSalt to sprinkle on food. Don't take potassium pills, or use salt substitute if you're taking certain blood pressure medications though ... check with your pharmacist or dr. first.
These are good, basic nutrient supplements for any person.