First of all, I would suggest doing extensive research into natural-remedies and be extremely cautious.
I understand that your original question was referring to the method, however I believe this information is relevant, as there are factors to take into account that suggest the method of direct ingestion may not be safe. Ultimately, you should contact a professional.
There is not enough scientific information to determine an appropriate range of doses for neem. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.
WebMD, not always accurate, does specify that Neem is taken orally, though it doesn't indicate what form (powder, leaf, pill, etc.). It has the following warnings and precautions about Neem in general:
Overview Neem is POSSIBLY SAFE for most adults when taken by
mouth for up to 10 weeks, when applied inside the mouth for up to 6
weeks, or when applied to the skin for up to 2 weeks. When neem is
taken in large doses or for long periods of time, it is POSSIBLY
UNSAFE. It might harm the kidneys and liver.
Taking neem seeds or oil by mouth is LIKELY UNSAFE for children. Serious side effects in infants and small children can happen within hours after taking neem oil. These serious side effects include vomiting, diarrhea, drowsiness, blood disorders, seizures,
loss of consciousness, coma, brain disorders, and death.
Pregnancy/Breast-Feeding Neem oil and neem bark are LIKELY
UNSAFE when taken by mouth during pregnancy. They can cause a
Not enough is known about the safety of need during breast-feeding.
Stay on the safe side and avoid use.
Auto-immune diseases Multiple sclerosis (MS), lupus (systemic
lupus erythematosus, SLE), rheumatoid arthritis (RA), or other similar
conditions: Neem may cause the immune system to become more active,
possibly increasing the symptoms of auto-immune diseases. If you
have one of these conditions, it’s best to avoid using neem.
Diabetes There is some evidence that neem can lower blood
sugar levels and might cause blood sugar to go too low. If you have
diabetes and use neem, monitor your blood sugar carefully. It might
be necessary to change the dose of your diabetes medication.
Infertility There is some evidence that neem can harm sperm.
It might also reduce fertility in other ways. If you are trying to
have children, avoid using neem.
Organ Transplant and Surgery There is a concern that neem
might decrease the effectiveness of medications that are used to
prevent organ rejection. Do not use neem if you have had an organ
Neem might also lower blood sugar levels as mentioned earlier. There
is a concern that it might interfere with blood sugar control during
and after surgery. Stop using neem at least 2 weeks before a
It would be safer to avoid direct leaf intake for children, the pregnant, and those trying to have a baby as well as those who have recently had a transplant.