Potassium phosphate intravenous infusion for adults

Who can administer

POTASSIUM phosphate

Infusions prepared at ward level using ampoules
- May be administered by registered competent doctor or nurse/midwife, PROVIDED the guidelines below (in Methods of Administration) have been adhered to

Important information

There are two separate monographs for IV phosphate- sodium phosphate or potassium phosphate- please ensure you are using the correct monograph
Caution with rate of administration (due to potassium content)
Suggest: Senior doctor review before administration of intravenous phosphate, as it's use can be dangerous
- Caution: the response to any given dose cannot be predicted, and IV use can cause hypocalcaemia (tetany), calcium-phosphate precipitation in the kidneys, and fatal arrhythmias ^{(ref 1)}
Patients with HYPOcalcaemia should have their calcium corrected before replacing phosphate ^{(ref 5)}
Patients with severe HYPERcalcaemia who require phosphate replacement: seek specialist advice ^{(ref 4)}
Renal impairment: Requires dose adjustment- see below
Give in a dedicated line as it may precipitate with other drugs

Available preparations

Phosphate salt	Volume	Phosphate content per vial/ampoule/bag	Sodium content per vial/ampoule/bag	Potassium content per vial/ampoule/bag
Potassium phosphate ampoule (Braun)	20ml	12mmol	nil	20mmol
Phosphate polyfusor pre-mixed bag - very severe hypophosphataemia. Supplied only on request.	500ml	50mmol	81mmol	9.5mmol

Reconstitution

Already in solution

Ampoules should be diluted further prior to administration

Addition of potassium phosphate concentrate to infusion bags

Preparation must be done jointly by a doctor and a nurse in the clinic room.
Both the Controlled Drug register, and the Additive label must be signed by the SAME doctor and nurse
UNUSED ampoules must immediately be returned to the CD press and signed back into the CD register by the SAME doctor and nurse
Clearly over-label the infusion bag to reflect the TOTAL amount of mmol of potassium phosphate
After adding potassium phosphate concentrate to an infusion bag, squeeze and invert bag a MINIMUM of ten times to avoid inadvertent administration of a toxic bolus

Infusion fluids

Sodium chloride 0.9% (preferred)

Glucose 5% may also be used if clinically appropriate

Methods of intravenous administration

Intermittent intravenous infusion (using an electronically controlled infusion device)

Administer as per guidelines below

Dose in adults

Table 1: Guidance on route given below but clinical judgement is always required ^{(ref 1)}
Route of administration	Phosphate level
Oral/enteral replacement	PREFERRED if >0.32mmol/L and asymptomatic or if level >0.48mmol/L and symptomatic
Intravenous route preferred	<0.32mmol/L or <0.48mmol and symptomatic or if unable to tolerate oral supplementation

Table 1: Guidance on route given below but clinical judgement is always required ^{(ref 1)}

Route of administration

Phosphate level

Oral/enteral replacement

PREFERRED if >0.32mmol/L and asymptomatic

if level >0.48mmol/L and symptomatic

Intravenous route preferred

<0.32mmol/L

<0.48mmol and symptomatic

if unable to tolerate oral supplementation

Table 2: POTASSIUM PHOSPHATE via peripheral line

Consider ONLY IF co-existing hypokalaemia

Preferable to treat hypophosphataemia and hypokalaemia separately using two individual infusion bags - rather than using Potasssium phosphate vial at all. This allows for the greatest amount of flexibility in the doses of both electrolytes

It is difficult to provide concrete guidelines for the treatment of severe hypophosphataemia as regimens vary greatly across hospitals in the UK and Ireland - we have tried to provide guidelines below but clinical judgment is always required

Use caution when interpreting phosphate levels. Changes in phosphate levels may be transient - treating underlying causes may be sufficient to correct level. Review medications which may contribute e.g. sevelamar, antacids, diuretics ^{(ref 5)}

The response to any given dose cannot be predicted, and IV use can cause hypocalcaemia (tetany), calcium-phosphate precipitation in the kidneys, and fatal arrhythmias ^{(ref 1)}

Prescribe dose in terms of phosphate dose required and then the phosphate salt required
- eg '12mmol phosphate as potassium phosphate'

Gentle replacement	Dose: 9mmol phosphate over 12 hours, and repeat as necessary ^{(ref 2,3)}
More individualised dosing ^{(ref 1)}	Level (mmol/L)	Phosphate dose	Maximum initial dose
	less than 0.32	0.4mmol/kg	48mmol phosphate
	0.33 to 0.44	0.3mmol/kg	30mmol phosphate
	>0.45	0.2mmol/kg	20mmol phosphate
Preparation	Doses up to 24mmol phosphate (40mmol potassium) Add to 500mL infusion fluid Doses 25 to 48mmol phosphate (40 ^(approx) to 80mmol potassium) Add to 1000mL infusion fluid For fluid restricted patients May be added to less volume provided the final concentration does not exceed 40mmol POTASSIUM per 500mL
Administration	Administer the required dose over 12 hours May administer more quickly - however cannot exceed a rate of administration of the POTASSIUM element of 10mmol/hour Doses of 36mmol phosphate or less may be administered over minimum 6 hours if clinically appropriate Doses greater than 36mmol phosphate MUST be administered over minimum 8 to 12 hours
Renal impairment	Use with great caution, consider specialist advice Generally avoid in severe renal impairment ^{(ref 6)}
Critical care/Fluid restriction	Higher doses and rates may apply in the Critical Care setting
Polyfusor	Available in Critical care areas- note however- only contains 9.5mmol potassium per polyfusor
Repeated doses	May require repeat infusions over subsequent days. Usual maximum is 50mmol phosphate per 24 hours
Switch to oral route	Consider switch to oral route once level >0.48mmol/L

Renal impairment

Use reduced doses with caution- see tables above

Monitoring

Monitor the following electrolytes every 6 to 12 hours: phosphate, calcium, potassium, sodium, magnesium
Monitor fluid balance and blood pressure
Monitor ECG

Storage

Potassium phosphate ampoules are treated as a controlled drug in GUHs (as it is a potasisum concentrate as well as containing phosphate). The routine supply of potassium phosphate is restricted to designated wards which are likely to be caring for critically ill patients
Phosphate Polyfusor is NOT treated as a controlled drug
Store below 25⁰C

References

Uptodate. Hypophosphataemia: Evaluation and Treatment March 2024. Accessed online 23/01/2025
Martindale- accessed online 23/01/2025
BNF- accessed online 23/01/2025
UpToDate Potassium Phosphate monograph - accessed March 2025
Maidstone and Tunbridge Wells NHS Trust 'Treatment of acute hypophosphataemia in adults. Review date August 2027
Local specialist opinion - email on file25/06/2025

These local guidelines were also consulted in the preparation of guide (to try and create a consensus from different sources)

Grampian staff guideline for the management of hypophosphataemia in adults July 2024
Worcestershire acute hospitals NHS Trust 'guideline for the treatment of hypophosphataemia in adults, March 2023
Liverpool University Hospitals NHS Trust
UKMI Leeds hospital 'How is acute hypophosphataemia treated in adults
Adults Therapeutic Handbook (NHS Greater Glasgow and Clyde), May 2023 Management of hypophosphataemia