While on the same dosage of Concerta, could it dramatically change the way it affects an ADHD person?

I've been on concerta for over 7 weeks now and I've been on a steady dose of 27 mg for the last 4. The first 3 weeks at 27 mg were very beneficial, but from the start of the 4th week, my ADHD has become worse. I feel so lethargic, can't concentrate, my eyes can barely stay open. I don't know what is going on. Could this be one of the uncommon side effects? please help, thanks.

I've been on concerta for over 7 weeks now and I've been on a steady dose of 27 mg for the last 4. The first 3 weeks at 27 mg were very beneficial, but from the start of the 4th week, my ADHD has become worse. I feel so lethargic, can't concentrate, my eyes can barely stay open. I don't know what is going on. Could this be one of the uncommon side effects? please help, thanks.

update: From what i've read, lethargy and drowsiness usually occur immediately after a change in dosage. But no variables have changed after the 3 weeks at the same 27 mg dosage except that my prescription was renewed. I asked my doctor for an increase in dosage because i still have difficulties with concentration and focus, but she wanted to keep me at the same dosage for some reasons she would not share.

Certainly lethargy and drowsiness can be caused by this drug. Something about the dose is obviously not right for you. 27mg isn't actually a high dose but it may be just more than you need, after all everyone responds differently. You need to go back to your doctor and talk with him, there is an 18mg capsule that might be better for you.