To much of a good thing.

When taking vitamin supplements it's important to recognize which vitamins may be harmful if taken in excess.

With so many different products to choose from it can become quite easy to "overdose" on a particular vitamin. 

Here are 10 different vitamins and minerals to monitor if you take supplements. 

1. Iron

Taking too much iron can lead to liver problems, accumulation of fluid in the lungs, fatigue, headache, low blood sugar, coma and testicular problems in men.

Daily Recommended Dietary Allowance (RDA): 8 mg for men, 18 mg for women (8 mg for women 51 and over)

Tolerable Upper Intake Levels (UL) (This is the highest dose adults can take without experiencing adverse effects): 45 mg/day 

2. Vitamin A

Excess vitamin A (even at just double the RDA) can increase the risk of birth defects and cause liver damage, reduced bone mineral density (which can lead to osteoporosis), and central nervous system disorders.

RDA: 3,000 IU (International Units) for men, 2,310 IU for women

UL: 10,000 IU/day

3. Vitamin C

Taking large amounts of vitamin C can lead to gastrointestinal upset and diarrhea. There are also reports (that have yet to be confirmed) that it may cause genetic mutations, birth defects, increased oxidative stress, kidney stones and even cancer.

RDA: 90 mg for men, 75 mg for women

UL: 2,000 mg/day

4. Calcium

Though rare, excessively high intakes of calcium can lead to hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals, including iron, zinc, magnesium, and phosphorus.

RDA: 1,000 mg for adults 19-50, 1,200 mg for those 

51 and over

UL: 2500 mg/day

5. Vitamin E

Because vitamin E is an anticoagulant, taking too much may increase the risk of bleeding problems. Also, according to the American Heart Association, excess amounts (even 400 IU/day or more) of this vitamin may increase the risk of death.

RDA: 22.5 IU

UL: 1,500 IU/day

6. Vitamin D

When taken in excess, vitamin D can raise blood levels of calcium, which can cause mental changes, such as confusion. It can also result in nausea, vomiting, poor appetite, constipation, weakness, and weight loss.

Adequate Daily Intake (AI) (used when there is not enough scientific evidence available to establish an RDA): 400 IU, 600 IU for those 71 and over

UL: 2,000 IU/day

7. Zinc

A zinc overdose (which can occur from as little as150 to 450 mg/day) can reduce immune function and good cholesterol levels, and alter iron function and copper levels.

RDA: 11 mg for men, 8 mg for women

UL: 40 mg

8. Selenium

In rare instances, too much selenium can result in a condition called selenosis (this occurs when selenium blood levels are greater than 100 µg/dL). Symptoms of selenosis include gastrointestinal upset, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage.

RDA: 55 µg

UL: 400 µg/day

9. Vitamin B6

At high doses (lower than 500 mg per day), vitamin B6 can result in nerve damage to the arms and legs.

RDA: 1.3 mg for those 19-50, 1.7 mg for men 51 and over, 1.5 mg for women 51 and over

UL: 100 mg/day

10. Copper

Taking too much copper can lead to organ damage (liver and kidneys) and neurologic problems. Other symptoms include weakness, abdominal pain, nausea, learning disabilities, memory lapses, diminished concentration, insomnia, seizure, delirium, stuttering and hyperactivity.

RDA: 900 mcg

UL: 10,000 mcg