Normal laboratory values (adult patients):
Calcium (Serum): 8.5 - 10.5 mg/dL (2.12 - 2.57 mmol/L )
Calcium (Ionized) Serum: 4.5 - 5.6 mg/dL (1.1-1.4 mmol/L)
Vitamin D and calcium requirements (RDA)
|
Body Calcium
99% in bone.
1% in ECF:
[50% in its free ionized form]
[40% complexed with albumin]
[10% complexed with anions such as phosphate.]
|
Less than 1% of the body's calcium is contained within the ECF, yet
this concentration is regulated carefully by the parathyroid hormone
and calcitonin. Parathyroid hormone is released by the
parathyroid gland in response to a low serum calcium level. It
increases resorption of bone (movement of Ca++ and PO4 out of the
bone); activates vitamin D, which increases the absorption of calcium
from the GIT; and simultaneously stimulates the kidneys to conserve
calcium and excrete phosphorus. Calcitonin is produced by the
thyroid gland when serum calcium levels are elevated (inhibits bone
resorption).
The ECF gains Ca++ from intestinal absorption and resorption from bones. It is lost from the ECF via secretion
into the GIT, urinary excretion, and deposition into bone.
Calcium is present in 3 different forms in the plasma: ionized, bound
and complexed. Only the ionized calcium is physiologically important.
The percentage of calcium that is ionized is affected by pH,
phosphorus, and albumin levels. The relationship between
ionized calcium and plasma pH is reciprocal (increase in pH decreases
percent of Ca++ ionized). Patients with alkalosis for example may
show signs of hypocalcemia despite a normal total calcium level.
Changes in albumin will affect total serum calcium without changing
the level of free calcium. (decreased albumin
 decreased
total Ca++
constant free Ca++)
Signs and symptoms:
Numbness with tingling of
fingers, extremities and circumoral region
hyperactive reflexes,
muscle cramps,
carpopedal
spasm,
stridor,
tetany,
seizures.
Positive Trousseau's sign (carpal
spasm with BP cuff) and positive Chvostek's sign (contraction of
facial and eyelid muscles when facial nerve tapped). Cardiac
effects include decreased myocardial contractility and heart failure.
History and risk factors:
1) Decreased ionized calcium: alkalosis;
administration of large quantities of citrated blood (may bind
calcium); hemodilution (volume replacement etc.)
2) Increased calcium loss in body fluids:
certain diuretics.
3)
Decreased intestinal absorption:
decreased intake; impaired vitamin D metabolism (renal failure);
chronic diarrhea, post-gastrectomy.
4) Hypoparathyroidism:
congenital or acquired.
5) Hyperphosphatemia:
e.g. renal failure. When hypocalcemia persists, it is best to delay
calcium supplementation until the serum phosphate level is below 6
mg/dL to reduce the risk of metastatic calcification.
6) Hypomagnesemia
(decreased PTH action and release). Chronic alcoholism; acute
pancreatitis. Hypocalcemia is difficult to correct without
first normalizing the serum magnesium concentration.
Diagnostic tests:
-Total serum calcium may be less than
8.5 mg/dl. Serum calcium levels should be evaluated with
serum albumin. For every 1.0 mg/dL drop in serum albumin, there
is a 0.8 - 1.0 mg/dL drop in the total calcium level.
-Ionized calcium will be less than 4.2
mg/dL. Symptoms of hypocalcemia usually occur when ionized levels
fall to <2.5 mg/dL.
-Parathyroid hormone: decreased levels
occur in hypoparathyroidism.
-Magnesium and phosphorus levels:
may be checked to indentify potential causes of hypocalcemia.
Treatment should be based on:
(1) Symptoms present: Paresthesias, tetany, carpopedal spasm,
seizures
(2) Signs: Chvosek's or Trousseau's signs, impaired cardiac
contractility, prolongation of the QT interval, bradycardia).
(3) Absolute level of calcium
(4) Rate of decrease (e.g. acute versus chronic decrease).
The therapeutic approach and management of hypocalcemia depends
largely on the severity of symptoms and the underlying cause.
In patients with asymptomatic hypocalcemia, it is important to verify
with repeat measurement (ionized or total calcium corrected for serum
albumin).
Calcium Conversions:
|
| Calcium Chloride |
1 gram (10ml)
= 273 mg elemental calcium
= 13.6 mEq
= 6.8 mmol. |
20mg of elemental calcium per mEq.
0.5 mmol of elemental calcium = 1.0 mEq. |
| Calcium Gluconate |
1 gram (10ml)
= 93 mg elemental calcium
= 4.65 mEq
= 2.325 mmol. |
20mg of elemental calcium per mEq.
0.5 mmol of elemental calcium = 1.0 mEq. |
| Example conversion: |
0.075 mmol elemental calcium/kg/hr = 0.15 mEq/kg/hr
= 3 mg/kg/hr. |
Vitamin D: Reference Intakes /
RDA
Source:
https://ods.od.nih.gov/factsheets/vitamind/Intake reference values for vitamin D and other
nutrients are provided in the Dietary Reference Intakes
(DRIs) developed by the Food and Nutrition Board (FNB)
at the Institute of Medicine of The National Academies
(formerly National Academy of Sciences). DRI is the
general term for a set of reference values used to plan
and assess nutrient intakes of healthy people. These
values, which vary by age and gender, include:
- Recommended Dietary Allowance (RDA): average
daily level of intake sufficient to meet the
nutrient requirements of nearly all (97%–98%)
healthy people.
- Adequate Intake (AI): established when
evidence is insufficient to develop an RDA and
is set at a level assumed to ensure nutritional
adequacy.
- Tolerable Upper Intake Level (UL): maximum
daily intake unlikely to cause adverse health
effects.
The FNB established an RDA for vitamin D
representing a daily intake that is sufficient to
maintain bone health and normal calcium metabolism
in healthy people. RDAs for vitamin D are listed in
both International Units (IUs) and micrograms (mcg);
the biological activity of 40 IU is equal to 1 mcg
(Table 2). Even though sunlight may be a major
source of vitamin D for some, the vitamin D RDAs are
set on the basis of minimal sun exposure.
Table 2:
Recommended Dietary Allowances (RDAs) for Vitamin D
| Age |
Male |
Female |
Pregnancy |
Lactation |
| 0–12 months* |
400 IU
(10 mcg) |
400 IU
(10 mcg) |
|
|
| 1–13 years |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
|
|
| 14–18 years |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
| 19–50 years |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
| 51–70 years |
600 IU
(15 mcg) |
600 IU
(15 mcg) |
|
|
| >70 years |
800 IU
(20 mcg) |
800 IU
(20 mcg) |
|
|
Calcium Supplementation Based on Age
Source:
https://ods.od.nih.gov/factsheets/Calcium-QuickFacts/
The amount of calcium you need each day depends on
your age. Average daily recommended amounts are listed
below in milligrams (mg):
| Birth to 6 months |
200 mg |
| Infants 7–12 months |
260 mg |
| Children 1–3 years |
700 mg |
| Children 4-8 years |
1,000 mg |
| Children 9–13 years |
1,300 mg |
| Teens 14–18 years |
1,300 mg |
| Adults 19–50 years |
1,000 mg |
| Adult men 51–70 years |
1,000 mg |
| Adult women 51–70 years |
1,200 mg |
| Adults 71 years and older |
1,200 mg |
| Pregnant and breastfeeding teens |
1,300 mg |
| Pregnant and breastfeeding
adults |
1,000 mg |
Upper limits - calcium:
Source:
https://ods.od.nih.gov/factsheets/Calcium-QuickFacts/The safe upper
limits for calcium are listed below. Most people do not get amounts
above the upper limits from food alone; excess intakes usually come
from the use of calcium supplements. Surveys show that some older
women in the United States probably get amounts somewhat above the
upper limit since the use of calcium supplements is common among
these women.
| Birth to 6 months |
1,000 mg |
| Infants 7-12 months |
1,500 mg |
| Children 1-8 years |
2,500 mg |
| Children 9-18 years |
3,000 mg |
| Adults 19-50 years |
2,500 mg |
| Adults 51 years and older |
2,000 mg |
| Pregnant and breastfeeding teens |
3,000 mg |
| Pregnant and breastfeeding
adults |
2,500 mg |
|
