Hi ,Fit,
I am sorry to say that you have been badly misinformed.
A level of 27 is just not lowish ,
it is very, very low , indeed so low , that if you were a child , then it could be expected that you might possibly be showing symptoms of rickets.
As an adult , then you would not get the same signs, your bones would not bend , but you might get bone pain.
Can I ask ? , do you drink milk , ? are you getting some calcium?. There is an adult condition known as osteomalacia... whereby too little vitamin d , can lead to poor bone maintenance, due to an inadequacy in calcium absorption.
From your description , then I would say , that you should definately supplement with vitamin D . It can help with many health problems.
I have posted on mumsnet , quite a bit about this problem, low Vit D.
Humans ..... throughout our evolution ... i.e.millions of years have had blood levels in the region of 120 - 140 , it is only in the last few hundreds of years that we have changed our environment to have much lower levels. In fact , in the last 40 years , we have very much reduced our levels ( here in the west - UK , etc. ) We keep out of the sun , we put on suncream/clothes that prevents sunlight reaching our skin , where most Vit D is made.
Please have a look at this conversation , where I tried to explain what is going on.
www.mumsnet.com/Talk/general_health/2421492-Vitimin-D-can-it-have-this-effect
it is a long read ... but lots of useful information.
Best of luck
BTBH
PS. I would recommend taking at least 3000 IU or 4000 IU per day , to raise your blood level by about 75- 85 nmol/l , whereby if you reach over 100 , then IF your symptoms are due to low Vit D , then after a few months ( not just weeks ) then you should see some improvements. It is not commonly known , that insomnia has also been associated with lack of Vit D, also depression .