Dietitian App

Biochemistry Reference Guide

Searchable biochemistry page with analyte cards, category filters, age-band filters, and reference-type badges so special cases such as local lab values, decision limits, and clinical targets are clearly separated from harmonised reference intervals.

Important: review these values against your local laboratory before clinical use. Some items are harmonised RIs, while others are RCPA page intervals, decision limits, or treatment targets.

Harmonised RIRCPA intervalLocal labDecision limitClinical target

Search analyte or keyword

Haemoglobin

Full blood count

Local labDraft

Unit

g/L

Specimen

Whole blood

Flags

3 tags

Clinical use

Screens for anaemia and helps assess oxygen-carrying capacity.

Nutrition relevance

Relevant in iron deficiency, B12/folate deficiency, inflammation, blood loss, and chronic disease.

Notes

RCPA does not provide a single harmonised Hb reference interval on the pathology test page. Use your local laboratory interval or WHO tables if you want diagnostic anaemia thresholds displayed.

AnaemiaIron deficiency workupGrowth / fatigue

Reference intervals / limits

Age band	Sex	Range	Comment
All ages	All	Consult local laboratory	RCPA directs users to local laboratory / WHO tables.

Ferritin

Iron studies

Decision limitDraft

Unit

µg/L

Specimen

Serum

Flags

3 tags

Clinical use

Assesses iron stores and supports interpretation of iron deficiency or overload.

Nutrition relevance

Key marker when reviewing low iron intake, poor intake variety, selective eating, heavy losses, or malabsorption.

Notes

Ferritin is handled by RCPA as decision limits rather than one harmonised reference interval. Upper limits are method dependent.

Iron deficiencySelective eatingInflammation can elevate

Reference intervals / limits

Age band	Sex	Range	Comment
Pre-pubescent child	All	≤20 µg/L	Diagnostic of iron deficiency.
Adult	All	≥30 µg/L to method upper limit	Healthy iron stores if no co-existing inflammatory disease or hepatocellular damage.
Upper reference limit	All	Method dependent	No harmonised upper ferritin RI is recommended by RCPA.

C-reactive protein

CRP

Inflammation

RCPA intervalDraft

Unit

mg/L

Specimen

Serum / plasma

Flags

2 tags

Clinical use

Assesses acute inflammation and can help contextualise ferritin and albumin.

Nutrition relevance

Useful when interpreting nutritional biochemistry in the setting of infection, inflammation, or acute illness.

InflammationInterpret ferritin carefully

Reference intervals / limits

Age band	Sex	Range	Comment
No age-band reference rows listed for this entry.

Sodium

Electrolytes / renal

Harmonised RIDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Assesses fluid balance, hydration, renal function, and sodium disorders.

Nutrition relevance

Important in dehydration, refeeding, fluid prescription, GI losses, and enteral/parenteral nutrition review.

HydrationFluid balanceGI losses

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	132–147 mmol/L	—
1w to <18y	All	133–144 mmol/L	—
18y to <120y	All	135–145 mmol/L	—

Potassium

Electrolytes / renal

Harmonised RIDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Assesses potassium status, renal function, acid-base issues, and cardiac risk.

Nutrition relevance

Relevant in vomiting, diarrhoea, refeeding, renal issues, and nutrition support monitoring.

Notes

Paediatric serum and paediatric plasma intervals differ. Adult interval is listed for both serum and plasma; labs using only heparin plasma may choose a lower interval.

RefeedingGI lossRenal monitoring

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	3.8–6.5 mmol/L	Serum.
1w to <26w	All	4.2–6.7 mmol/L	Serum.
26w to <2y	All	3.9–5.6 mmol/L	Serum.
2y to <18y	All	3.6–5.3 mmol/L	Serum.
0d to <1w	All	3.5–6.2 mmol/L	Plasma.
1w to <26w	All	3.8–6.4 mmol/L	Plasma.
26w to <2y	All	3.5–5.4 mmol/L	Plasma.
2y to <18y	All	3.3–4.9 mmol/L	Plasma.
18y to <120y	All	3.5–5.2 mmol/L	Adult serum / plasma interval.

Creatinine

Electrolytes / renal

Harmonised RIDraft

Unit

µmol/L

Specimen

Serum / plasma

Flags

2 tags

Clinical use

Used to assess renal function, especially alongside urea and electrolytes.

Nutrition relevance

Important when prescribing fluids, protein, enteral feeds, or disease-specific formulas.

Notes

RCPA notes these creatinine intervals are by Vitros enzymatic assay and are harmonised for adults up to 60 years.

Renal functionProtein prescription

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	22–93 µmol/L	—
1w to <4w	All	17–50 µmol/L	—
4w to <2y	All	11–36 µmol/L	—
2y to <6y	All	20–44 µmol/L	—
6y to <12y	All	27–58 µmol/L	—
12y to <15y	Male	35–83 µmol/L	—
15y to <19y	Male	50–100 µmol/L	—
19y to <60y	Male	60–110 µmol/L	—
12y to <15y	Female	35–74 µmol/L	—
15y to <19y	Female	38–82 µmol/L	—
19y to <60y	Female	45–90 µmol/L	—

Albumin

Liver function

RCPA intervalDraft

Unit

g/L

Specimen

Serum

Flags

3 tags

Clinical use

Reflects hepatic synthesis and is influenced by inflammation, illness, and fluid status.

Nutrition relevance

Not a standalone nutrition marker, but useful in clinical context, especially with inflammation and disease severity.

Notes

RCPA lists this as age dependent and advises laboratory-specific interpretation.

Inflammation affectedFluid shiftsClinical context required

Reference intervals / limits

Age band	Sex	Range	Comment
All ages	All	32–45 g/L	Age dependent.

Alanine aminotransferase

ALT

Liver function

Harmonised RIDraft

Unit

U/L

Specimen

Serum

Flags

2 tags

Clinical use

Assesses hepatocellular injury and liver involvement.

Nutrition relevance

Relevant when reviewing obesity, NAFLD risk, medication interactions, and complex feeding issues.

Notes

The harmonised table provides adult values here; paediatric harmonised ALT intervals are not shown in Table 6.

Liver reviewNAFLD context

Reference intervals / limits

Age band	Sex	Range	Comment
18y to <120y	Male	5–40 U/L	—
18y to <120y	Female	5–35 U/L	—

Alkaline phosphatase

ALP

Bone / minerals

Harmonised RIDraft

Unit

U/L

Specimen

Serum

Flags

3 tags

Clinical use

Associated with bone growth and turnover, and also reflects hepatobiliary issues.

Nutrition relevance

Helpful in bone health, vitamin D review, growth assessment, and interpretation during periods of rapid growth.

Notes

Paediatric values vary substantially with age and pubertal stage.

Bone healthGrowthVitamin D context

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	80–380 U/L	—
1w to <4w	All	120–550 U/L	—
4w to <26w	All	120–650 U/L	—
26w to <2y	All	120–450 U/L	—
2y to <6y	All	120–370 U/L	—
6y to <10y	All	120–440 U/L	—
10y to <14y	Male	130–530 U/L	—
14y to <15y	Male	105–480 U/L	—
15y to <17y	Male	80–380 U/L	—
17y to <19y	Male	50–220 U/L	—
19y to <22y	Male	45–150 U/L	—
22y to <120y	Male	30–110 U/L	—
10y to <13y	Female	100–460 U/L	—
13y to <14y	Female	70–330 U/L	—
14y to <15y	Female	50–280 U/L	—
15y to <16y	Female	45–170 U/L	—
16y to <22y	Female	35–140 U/L	—
22y to <120y	Female	30–110 U/L	—

Calcium

Bone / minerals

Harmonised RIDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Assesses calcium status in conjunction with phosphate, magnesium, vitamin D, and PTH where relevant.

Nutrition relevance

Important for bone health, restricted diets, allergy exclusion diets, and long-term nutrition support.

Bone healthRestricted dietsVitamin D context

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	1.85–2.80 mmol/L	—
1w to <26w	All	2.20–2.80 mmol/L	—
26w to <2y	All	2.20–2.70 mmol/L	—
2y to <18y	All	2.20–2.65 mmol/L	—
18y to <120y	All	2.10–2.60 mmol/L	—

Phosphate

Bone / minerals

Harmonised RIDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Assesses phosphate balance and is important in bone metabolism and refeeding risk.

Nutrition relevance

A core marker during refeeding, malnutrition recovery, and nutrition support monitoring.

RefeedingBone healthNutrition support

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	1.25–2.85 mmol/L	—
1w to <4w	All	1.50–2.75 mmol/L	—
4w to <26w	All	1.45–2.50 mmol/L	—
26w to <1y	All	1.30–2.30 mmol/L	—
1y to <4y	All	1.10–2.20 mmol/L	—
4y to <15y	All	0.90–2.00 mmol/L	—
15y to <18y	All	0.80–1.85 mmol/L	—
18y to <20y	All	0.75–1.65 mmol/L	—
20y to <120y	All	0.75–1.50 mmol/L	—

Magnesium

Bone / minerals

Harmonised RIDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Monitors magnesium status, especially in GI losses, renal issues, and refeeding.

Nutrition relevance

Useful in malnutrition, refeeding, feeding intolerance, diarrhoea, and nutrition support review.

RefeedingGI lossNutrition support

Reference intervals / limits

Age band	Sex	Range	Comment
0d to <1w	All	0.60–1.00 mmol/L	—
1w to <18y	All	0.65–1.10 mmol/L	—
18y to <120y	All	0.70–1.10 mmol/L	—

25-OH Vitamin D

Vitamin D

Vitamins / trace elements

RCPA intervalDraft

Unit

nmol/L

Specimen

Serum

Flags

3 tags

Clinical use

Assesses vitamin D status and supports bone health assessment.

Nutrition relevance

Important in restricted diets, low sunlight exposure, bone health concerns, and chronic disease.

Bone healthRestricted dietsSupplement review

Reference intervals / limits

Age band	Sex	Range	Comment
No age-band reference rows listed for this entry.

Vitamin B12

B12

Vitamins / trace elements

RCPA intervalDraft

Unit

pmol/L

Specimen

Serum

Flags

3 tags

Clinical use

Assesses B12 status in the context of macrocytosis, low intake, or malabsorption.

Nutrition relevance

Relevant for vegan diets, food refusal, restrictive intake, GI disease, and deficiency workup.

Restrictive eatingVegan dietMacrocytosis

Reference intervals / limits

Age band	Sex	Range	Comment
All ages	All	120–1000 pmol/L	May vary by laboratory.

Folate

Vitamins / trace elements

RCPA intervalDraft

Unit

nmol/L

Specimen

Serum

Flags

2 tags

Clinical use

Assesses folate status in anaemia workup and low dietary variety.

Nutrition relevance

Useful in poor intake, selective eating, GI disease, and macrocytic anaemia review.

Selective eatingAnaemia workup

Reference intervals / limits

Age band	Sex	Range	Comment
No age-band reference rows listed for this entry.

Zinc

Vitamins / trace elements

RCPA intervalDraft

Unit

µmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Assesses zinc status, keeping in mind that interpretation can be affected by inflammation and timing.

Nutrition relevance

Relevant in poor growth, restricted intake, GI conditions, and prolonged inadequate nutrition.

GrowthRestricted dietsInflammation affects interpretation

Reference intervals / limits

Age band	Sex	Range	Comment
All ages	All	10–20 µmol/L	May vary by laboratory. Diurnal variation occurs.

Total cholesterol

Cholesterol

Lipids / metabolic

Clinical targetDraft

Unit

mmol/L

Specimen

Serum / plasma

Flags

3 tags

Clinical use

Used in lipid review and cardiometabolic risk assessment.

Nutrition relevance

Useful in obesity, dyslipidaemia, family history review, and therapeutic diet planning.

DyslipidaemiaObesityFamily history

Reference intervals / limits

Age band	Sex	Range	Comment
No age-band reference rows listed for this entry.