Some people have problems with vitamin D

What is the most important information I should know about cholecalciferol?

Do not use this medication if you have ever had an allergic reaction to vitamin D, or if you have high levels of calcium or vitamin D in your blood, or if you have any condition that makes it hard for your body to absorb nutrients from food (malabsorption). Before taking cholecalciferol, tell your doctor if you are allergic to any drugs or if you have heart disease, kidney disease, or an electrolyte imbalance.
Do not take other vitamin or mineral supplements unless your doctor has told you to. Avoid using calcium supplements or antacids without your doctor's advice. Use only the specific type of supplement or antacid your doctor recommends. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.
Seek emergency medical attention if you think you have used too much of this medicine. An overdose of vitamin D can cause serious or life-threatening side effects. Overdose symptoms may include headache, weakness, drowsiness, dry mouth, nausea, vomiting, constipation, muscle or bone pain, metallic taste in the mouth, weight loss, itchy skin, changes in heart rate, loss of interest in sex, confusion, unusual thoughts or behavior, severe pain in your upper stomach spreading to your back, or fainting.

What should I discuss with my healthcare provider before taking cholecalciferol?

Do not use this medication if you have ever had an allergic reaction to vitamin D or if you have: Your cholecalciferol dose needs may change if you are pregnant or breastfeeding. Tell your doctor if you are pregnant or plan to become pregnant during treatment or if you are breastfeeding a baby.

How should I take cholecalciferol?

Take this medication exactly as directed on the label or as prescribed by your doctor. Do not take it in larger amounts or for longer than recommended.
Your doctor may occasionally change your dose to make sure you get the best results from this medication.
Cholecalciferol is only part of a complete program of treatment that may also include a special diet. It is very important to follow the diet plan created for you by your doctor or nutrition counselor. You should become very familiar with the list of foods you must eat or avoid to help control your condition.
Store this medication at room temperature, away from moisture, light, and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. If it is almost time for your next dose, wait until then to take the medicine and skip the missed dose. Do not take extra medicine to make up for the missed dose.

What happens if I overdose?

Seek emergency medical attention if you think you have used too much of this medicine. An overdose of vitamin D can cause serious or life-threatening side effects. Overdose symptoms may include headache, weakness, drowsiness, dry mouth, nausea, vomiting, constipation, muscle or bone pain, metallic taste in the mouth, weight loss, itchy skin, changes in heart rate, loss of interest in sex, confusion, unusual thoughts or behavior, severe pain in your upper stomach spreading to your back, or fainting.

What should I avoid while taking cholecalciferol?

Do not take other vitamin or mineral supplements unless your doctor has told you to. Avoid using calcium supplements or antacids without your doctor's advice. Use only the specific type of supplement or antacid your doctor recommends.

What are the possible side effects of cholecalciferol?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop taking cholecalciferol and call your doctor at once if you have a serious side effect such as:

thinking problems, changes in behavior, feeling irritable;
urinating more than usual;
chest pain, feeling short of breath; or
early signs of vitamin D overdose

(weakness, metallic taste in your mouth, weight loss, muscle or bone pain, constipation, nausea, and vomiting).
This is not a complete list of side effects, and others may occur. Tell your doctor about any unusual or bothersome side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect cholecalciferol?

Before taking cholecalciferol, tell your doctor if you are taking any of the following medicines:

seizure medication;
cholestyramine (Prevalite, Questran);
colestipol (Colestid);
steroids (prednisone and others);
digoxin (digitalis, Lanoxin); or
a diuretic (water pill) such as chlorothiazide (Diuril), hydrochlorothiazide (HCTZ, HydroDiuril, Hyzaar, Lopressor, Vasoretic, Zestoretic), chlorthalidone (Hygroton, Thalitone), indapamide (Lozol), metolazone (Mykrox, Zaroxolyn), and others.

This list is not complete, and there may be other drugs that can interact with cholecalciferol. Tell your doctor about all your prescription and over-the-counter medications, vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start a new medication without telling your doctor.

Another list

Vitamin D3 has sometimes caused these symptoms, but the percentage of occurrences is unknown.
Please note: no drug should be ruled out as causing symptoms, even if the symptom is not listed.

Abdominal cramps
Abnormal kidney function
Allergic reactions (may include a sudden severe drop in blood pressure; rapid heart rate; skin rash, itching, hives; itchy, runny, congested nose; red itchy, watery eyes; shortness of breath, wheezing, cough, hoarseness, chest tightness; nausea, vomiting, abdominal cramps, diarrhea; irritation of the stomach and esophagus)
Anorexia/loss of appetite (anorexia is a medical term for loss of appetite - sometimes used for anorexia nervosa, the eating disorder)
Behavior changes - after medication overdose
Bone pain - after medication overdose
Calcium deposits in abnormal locations where there is no bone - may be visible on x-ray)
Chest pain or tightness - after medication overdose
Coma
Confusion/disorientation
Constipation - after medication overdose
Coordination problems ("ataxia")
Difficulty thinking - after medication overdose
Dry mouth
- comment by VitaminDWiki - appears to be due to low Magnesium or low Vitamin B12
Excessive urination
Excessive, prolonged thirst
Frequent wakening at night to urinate
Headache
High blood pressure
High/increased calcium levels
Inability to comprehend language - after medication overdose
Irregular/abnormal heart rate
Irritability - after medication overdose
Itching
Lack of energy/fatigue
Metallic taste - after medication overdose
Muscle pain/soreness - after medication overdose
Muscle weakness - after medication overdose
Nausea - after medication overdose
Overdose of vitamin D (may cause high blood levels of calcium with mental status changes/confusion, calcium deposits in abnormal/non-bone locations, and abnormal heart rhythm; high levels of phosphate; increased calcium in the urine; nausea/vomiting; poor appetite; weakness; weight loss) - after medication overdose
Protein in the urine
Ringing in the ears
Seizure
Shortness of breath - after medication overdose
Vertigo (dizziness, loss of balance, feeling that the room is spinning)
Vomiting - after medication overdose
Weight loss - after medication overdose