Fifty
There should be absolutely no problem taking a supplement without the test. Just so you know, the I.O.M.( Institute of medicine in USA) have recently looked at Vit D safety and supplementation levels. Their tolerable intake level is up to 4000 IU per day. Their NOAL (no adverse event level) is 10,000 IU per day. However no toxicity has ever been found below 30,000 I U per day for adults.
Most people respond to supplement (make sure it is D3 ) by raising their blood level by about 25 nmol/L per 1000 IU of daily dose. If you are short of Vit D then a few thousand units per day would be fine. Do not be tempted to dose weekly , with ultra high doses , as it is not so beneficial to your body dosing that way. Daily is much preferred. After all that is the way we naturally got vitamin D , for millions of years, out in the sun , daily.
Throughout evolution , and even now, humans living an ancestral lifestlyle have blood levels of 120 - 140 nmol/Litre. We here in the UK, keeping indoors, with our high latitude cannot make much , and so, many people are deficient, usually 30 - 50 ish. nmol/L. The current guidlines suggest that 50 is normal, that however is only because that is around the average for people here, the real normal , is that level we evolved to have over millions of years. Other primate species have those levels as well.
It will take several months to have an effect on your bone ( if that is your problem ). Physiologically we require about 70 IU per day per kilogram of body weight. That would be from all sources, including sun, food and supplements. It would be a good thing to get your level checked though. At this time of year , you will be close to your minimum, after a winter of no sun. It will give you an idea how much to take, over the longer term. If your level is very low, then you could consider a loading dose , ie. double your maintenance dose , for a few weeks daily. Although that would be difficult to do , without knowing your current level.
The contra indications of high dose , would be sarcoidosis or granulomatosis disease , if you have that, then see a doctor before taking anything. They are very very rare though.
BTBH