hi whowantsadog ,
IF you respond as an average adult , then IF you take 1000 IU daily , then your blood level of Vitamin D will rise by 25 nmol/litre after about 2 to 3 months.
It is generally recommended, by Vitamin D researchers, that your blood level should be around 100 -150 , for optimum health. This is regarded as within the normal band , even by the NHS in the UK. By normal , I mean a healthy level. Very many people are well below this level , in fact most people in the UK are at about 1/2 to 1/3 of that level. Particularly in winter, when the sunlight at our latitude ( UK) is not strong enough to make any vitamin D in our skin. In addition , many people use sunscreen , in strong sunlight , which stops your skin making any vitamin D , even in summer. It is no surprise that most people are low.
Typical symptoms would be , tiredness, lethargy , bone and muscular pain , increased susceptibility to infections both viral and bacterial, etc etc.
IF your level was sub 30 , then in order to get to where I have indicated , it would be eminently acceptable to take 5000 IU per day , in the long term . review after 3 months say , and if your level is between 100 - 150 , then continue with that dose , if it is somewhat above , then maybe drop down a thousand or two. IF you simply stop taking any supplement , then your level will just drop to your current level in about 4- 6 months after stopping. ( unless you make lifestyle changes )
have a look at these threads , which you should find interesting ...
www.mumsnet.com/Talk/general_health/2421492-Vitimin-D-can-it-have-this-effect
where we discuss Vitamin D , many people's experiences, doses, etc. It is a long read , but should be of some help.
Also , for bone and muscular pain , have a look here ,
www.mumsnet.com/Talk/general_health/2377129-Quick-Self-Check-for-Vitamin-D-deficiency
best of luck, I hope this is helpful !
BTBH