Even to much vitamin D can be problematic.

Vitamin D toxicity usually results from taking an excessive amount of vitamin D supplements — not from your diet or too much sun exposure. That's because your body produces only a limited amount of vitamin D from sun exposure, and even fortified foods don't contain large amounts of vitamin D. Although vitamin D toxicity is rare even among people who take supplements, you may be at greater risk if you have health problems, such as liver or kidney conditions, or if you take thiazide-type diuretics.
The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), causing symptoms such as:

Nausea
Vomiting
Poor appetite
Constipation
Weakness
Confusion
Heart rhythm abnormalities
Kidney stones

Treatment of vitamin D toxicity may include:

Stopping vitamin D supplements
Restricting calcium intake
Medications
Hydration with fluids
Hospitalization in severe cases

How Much Vitamin D Do You Need?
How much vitamin D you need depends on your age and risk factors. Recommendations for daily adequate intake, which are being reviewed, are 200 IU for adults under 50, 400 IU for ages 51 to 70, and 600 IU for ages 70 or over. Most experts, though, feel those levels are too low. The National Osteoporosis Foundation recommends 800 to 1,000 IU for all adults over age 50.