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Overview: Potassium phosphate/sodium phosphate is a form of phosphorus. It is used for low phosphorus levels and certain types of kidney stones, among other uses. It works by increasing the amount of phosphorus in the body and the amount of acid in urine, which makes it harder for kidney stones to form. The most common side effects are nausea, vomiting, diarrhea, and stomach pain.

Uses

What is potassium phosphate/sodium phosphate used for?

Potassium phosphate/sodium phosphate is commonly used for the following conditions.

  • Low phosphorus levels (hypophosphatemia)
  • Certain types of kidney stones
  • Reduce the smell and irritation caused by high levels of ammonia in urine (pee)

Potassium phosphate/sodium phosphate may also be used for other conditions as determined by your health care provider.

Note: The FDA has not reviewed this medicine for safety and effectiveness, and the label is not approved by the FDA. Learn more about unapproved drugs here.

How does potassium phosphate/sodium phosphate work (mechanism of action)?

Potassium phosphate/sodium phosphate is a form of phosphorus. Taking this medicine helps to increase phosphorus levels. 

Potassium phosphate/sodium phosphate also helps to increase the amount of acid in your urine (pee). This makes it harder for kidney stones to form or for bacteria to survive. It also helps to reduce the smell and irritation caused by ammonia in urine.

How is potassium phosphate/sodium phosphate supplied (dosage forms)?

Brands and other names

  • K-Phos M.F.
  • K-Phos Neutral
  • K-Phos No.2
  • Neutra-Phos
  • Phos-NaK
  • Phospha 250 Neutral
  • Phospho-Trin 250 Neutral
  • Uro-KP Neutral

Dosage forms and strengths

  • 250 mg of phosphorus per oral tablet

How should I store potassium phosphate/sodium phosphate?

Potassium phosphate/sodium phosphate should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place and keep the container tightly closed.

Side Effects

What are the most common side effects of potassium phosphate/sodium phosphate?

The most common side effects of potassium phosphate/sodium phosphate are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea or vomiting
  • Diarrhea
  • Stomach pain

There may be other side effects of potassium phosphate/sodium phosphate that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of potassium phosphate/sodium phosphate?

While less common, the most serious side effects of potassium phosphate/sodium phosphate are described below, along with what to do if they happen.

Severe Allergic Reactions. Potassium phosphate/sodium phosphate may cause allergic reactions, which can be serious. Stop taking potassium phosphate/sodium phosphate and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Electrolyte Changes. Potassium phosphate/sodium phosphate may cause changes in the levels of certain minerals in your body called electrolytes. For example, it may cause high potassium levels (hyperkalemia), high phosphorus levels (hyperphosphatemia), or low calcium levels (hypocalcemia). These changes can be serious. The risk is higher in people who take certain other medicines or who have certain health problems. Keep appointments for blood tests so that your health care provider can check your electrolyte levels. Call your health care provider if you have any of the following symptoms of electrolyte changes.

  • Muscle cramps, spasms, or unwanted movements
  • Muscle weakness or unusual tiredness
  • Slow heartbeat or a feeling of skipped heartbeats
  • Nausea or vomiting
  • Trouble breathing
  • Abnormal heart rhythm
  • Bone and joint pain
  • Rash or itching
  • Numbness or tingling around the mouth

Fluid Retention (Edema). Each 250 mg dose of potassium phosphate/sodium phosphate contains about 300 mg of sodium. For people who are sensitive to sodium or who are on a low-sodium diet, this may cause fluid retention and swelling. Fluid retention can cause serious issues in people with certain conditions, such as heart failure or kidney disease. Call your health care provider right away if you have any of the following symptoms.

  • Chest pain
  • Irregular heartbeat
  • Shortness of breath
  • Stretched or shiny skin
  • Swollen body parts, such as the belly or ankles

Warnings & Precautions

Who should not use potassium phosphate/sodium phosphate?

Allergies to Ingredients. People who are allergic to any of the following should not take potassium phosphate/sodium phosphate.

  • K-Phos M.F.
  • K-Phos Neutral
  • K-Phos No.2
  • Neutra-Phos
  • Phos-NaK
  • Phospha 250 Neutral
  • Phospho-Trin 250 Neutral
  • Potassium phosphate/sodium phosphate
  • Uro-KP Neutral
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific potassium phosphate/sodium phosphate products they stock.

High Phosphorus Levels. You should not take potassium phosphate/sodium phosphate if you have high phosphorus levels.

Serious Kidney Problems. If you have serious kidney problems, you should not take potassium phosphate/sodium phosphate.

Certain Kidney or Bladder Infections. Certain types of infections can cause phosphate stones to form in the kidneys. If you have phosphate stones caused by one of these infections, you should not take potassium phosphate/sodium phosphate.

What should I know about potassium phosphate/sodium phosphate before using it?

Do not take potassium phosphate/sodium phosphate unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share potassium phosphate/sodium phosphate with other people, even if they have the same condition as you. It may harm them.

Keep potassium phosphate/sodium phosphate out of the reach of children.

Potassium phosphate/sodium phosphate should be taken with a full glass of water and a meal.

If you are taking potassium phosphate/sodium phosphate for kidney stones, you may still pass old stones that were already present before you started this medicine. This medicine works by helping to prevent new stones from forming.

Each 250 mg dose of potassium phosphate/sodium phosphate contains about 300 mg of sodium. If you are sensitive to sodium or are on a low-sodium diet, you may need to make changes to your diet while taking potassium phosphate/sodium phosphate.

Your health care provider may monitor your blood levels while you are taking potassium phosphate/sodium phosphate. Keep all appointments for blood tests and other tests. 

What should I tell my health care provider before using potassium phosphate/sodium phosphate?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if potassium phosphate/sodium phosphate is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Other Medicines and Supplements. Potassium phosphate/sodium phosphate may interact with other medicines and supplements. Before taking potassium phosphate/sodium phosphate, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how potassium phosphate/sodium phosphate could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take potassium phosphate/sodium phosphate while you are pregnant or trying to get pregnant.

Breastfeeding. It is not known if potassium phosphate/sodium phosphate passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take potassium phosphate/sodium phosphate while breastfeeding.

Interactions

Does potassium phosphate/sodium phosphate interact with foods or drinks?

There are no known interactions between potassium phosphate/sodium phosphate and foods or drinks. Taking this medicine with food can help reduce side effects.

It is unknown if drinking alcohol will affect potassium phosphate/sodium phosphate.

Does potassium phosphate/sodium phosphate interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking potassium phosphate/sodium phosphate.

  • An antacid or supplement containing aluminum, calcium, or magnesium
  • A supplement or medicine containing Vitamin D (cholecalciferol, ergocalciferol)
  • A corticosteroid, such as dexamethasone, methylprednisolone, or prednisone, which is a medicine for certain inflammatory conditions 
  • A medicine for high blood pressure
  • Amiloride (Midamor), eplerenone (Inspra), spironolactone (Aldactone, Carospir), or triamterene (Dyrenium), which are types of diuretics, also called water pills
  • Corticotropin (ACTH, Acthar), which is a medicine used for multiple sclerosis
  • Potassium chloride (Klor-Con and others), which is a medicine used to raise potassium levels
  • A supplement or salt substitute containing potassium
  • Aspirin, which is in many prescription and OTC products, including those for pain, swelling, and fever
  • A salicylate, such as diflunisal or salsalate, which is a medicine used for osteoarthritis or rheumatoid arthritis

This may not be a complete list of medicines that can interact with potassium phosphate/sodium phosphate. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much potassium phosphate/sodium phosphate?

If you or someone else has used too much potassium phosphate/sodium phosphate, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of potassium phosphate/sodium phosphate?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.