Potassium and phosphate are the main focus of dialysis nutrition. But what about after transplantation and what guidelines apply here? Is a low-phosphate and low-potassium diet important here too, or do other rules apply?
Potassium and phosphate are indispensable in your body and it is hard to imagine life without them. It is therefore all the more important that you supply your body with sufficient potassium and phosphate. Potassium is an important basic building block of all your body cells and regulates, for example, the fluid content in a cell. Potassium is also responsible for the transmission of impulses in your nerves, i.e. communication in your body. It is also involved in the control of your muscles. Almost 99% of your body's total potassium is in your body cells and only 1% is in your blood.
Phosphate, together with calcium, is responsible for a functioning bone metabolism. So simply put, it regulates the balance between bone formation and bone breakdown. This ensures that your bones stay fit. But phosphate is also an important building block for your energy metabolism and for your genetic makeup in the body.
Can my new kidney rebalance potassium & phosphate?
During your time on dialysis, potassium and phosphate were the eternal pests. The rule makers, the ones with the strict bans. Good news - this gradually changes after transplant!
If your new kidney is working well, phosphate will be absorbed from your diet through your intestines. This excess is filtered out and excreted by your transplanted kidney. So your phosphate levels will be back in balance. The same is true for your potassium. Although your new kidney should be able to balance your potassium levels after a short recovery period, this may take some time after the transplant. So, be sure to regularly and proactively discuss with your treating medical team when and which systems are functioning again with your new kidney.
It can even happen that your new kidney filters too much phosphate or potassium from your blood, which is then accompanied by low values in your blood. In this case, it is called hypokalemia or hypophosphatemia. Low phosphate levels can lead to muscle weakness. In severe cases, severe phosphate deficiency can also cause difficulty breathing, heart failure, or seizures. On the other hand, if your potassium level is too low, it can sometimes show up as muscle weakness, cramps, or muscle paralysis. A low potassium level, like a high one, can also lead to heart palpitations and arrhythmias.
Optimally, however, transplantation restores stable blood levels of potassium and phosphate. However, this is not always the case immediately, especially shortly after transplantation, because the new kidney needs a bit of start-up time
What are approximate target values for potassium & phosphate in transplant recipients?
After transplantation, the approximate normal range for potassium in blood plasma is between 3.5 and 5.0 mmoL per liter. Your phosphate levels should generally be between 0.84 - 1.45 mmol/l (or 2.5 - 4.5 mg/dl). By the way, these normal ranges can be slightly different from lab to lab.
It's best to ask what it is at your center. Potassium above 5.0 mmoL per liter (or above the upper normal range) is called hyperkalemia. At a potassium level above 5.9 mmoL per liter, you have moderate to severe hyperkalemia, which should be treated quickly. Values above 6.5 mmol per liter are always severe hyperkalemia and very dangerous. This remains unchanged even after transplantation.
Here is a summary of the most important target values once again:
- Target value for phosphate after transplantation: 0.84 - 1.45 mmol/l (or 2.5 - 4.5 mg/dl)
- Target value for potassium after transplantation: 3.5 and 5.0 mmoL/l
Danger zones for your potassium:
- Mild hyperkalemia: 5.0 - 5.94 mmoL/l
- Moderate to severe hyperkalemia: 6.0 - 6.4 mmoL/l
- Severe hyperkalemia: ≥ 6.5 mmol/L
Do I feel that my potassium or phosphate is too high or too low?
If your new kidney is not yet working quite as you had hoped after transplantation, it can happen that both phosphate and potassium levels rise again. In these cases, it is called hyperkalemia or hyperphosphatemia.
Too much phosphate in the body rarely leads to immediate symptoms. The parameter also changes rather slowly in your blood count. Over time, however, the noticeable consequences are the occlusion or narrowing of your arteries, which leads to insufficient blood flow in the affected areas of the body. The death of skin - so-called necrosis - can also occur. So phosphate is often not so wild in the short term, but can be very dangerous in the long term.
Mild potassium excess can be treacherous because it doesn't necessarily cause symptoms. Sometimes it can bring signs such as tingling or numbness of the skin, diarrhea or muscle weakness. In more serious cases, muscle paralysis is sometimes reported. If the potassium rises to high levels, this can lead to very dangerous heart palpitations and cardiac arrhythmias.
Reading this paragraph, I'm sure you realize why potassium and phosphate can be dangerous after all: Since you often don't necessarily feel a mild increase in your levels strongly and immediately, you should also make sure as a transplant recipient that your levels are in the green zone - even if you feel good.
How much potassium and phosphate should I consume daily?
For people with healthy kidneys, a complete mixed diet including beverages contains approximately 4,700 mg of potassium per day. After transplant, your potassium intake should be based on your lab values. While you can follow the guidelines for healthy people for normal potassium levels, a maximum daily guideline of 3,000 mg is often recommended for excess potassium, depending on your blood potassium and GFR range.
For kidney-healthy individuals, the German Nutrition Society (DGE) recommends a phosphate intake of 700 mg per day. The international nephrological guidelines (=KDIGO) recommend a low phosphate diet with guideline values between 600 - 1000 mg per day in case of early-stage kidney disease. So you realize that regardless of the function of your kidneys, a relatively low upper limit for your daily phosphate intake is reasonable. After transplantation, you can also follow the first mentioned guideline for healthy kidneys.
For an exact adjustment of your daily guideline value you should in any case talk to your medical team and your nutritionist. These are always based on your current blood values and should always be determined in consultation with your medical team. In most cases, after a kidney transplant, you no longer have to pay attention to certain maximum daily amounts.
What should I do if my values vary?
If your kidney or lab values change after transplantation, adjustments to your diet might be considered. The same is true for your potassium and phosphate intake. However, unlike dialysis, it is not always necessary to restrict your intake for these two nutrients. It may also be that your new kidney is removing too much potassium and phosphate from your blood and you should therefore increase your intake. Adjustments are always individualized and should always be discussed with your medical team.
1. What to do if my potassium and phosphate levels are out of range?
Whether your levels are too high or too low, your diet will often help you get them back under control. This includes choosing the right foods. Potassium and phosphate are found in all foods. As a transplant recipient, it is important to be aware of which foods are high in potassium and phosphate and which are low.
In addition to your diet, your medications can also affect your potassium or phosphate levels. If your potassium or phosphate levels are not within the target range, it is always worth taking a look at your medication. However, this is always done by your medical team.
Depending on your potassium and phosphate levels, you can, in consultation with your medical team, set your daily guideline values in the settings of the Mizu app. This will help you better interpret the foods in the app.
2. What to do if my kidney function values vary?
The key point for fluctuations in your potassium or phosphate levels is almost always the function of your new kidney. So, as always after a transplant, the most important thing is to take care of your new organ and follow the right behaviors and diet. You can find tips and tricks for this in many articles in the Mizu App. In particular, a deterioration in your transplant function may require you to restrict your potassium and phosphate intake.
In some cases, especially right after the transplant, dialysis can help keep your lab values in balance until your new kidney is fully ready for action. Don't worry, this is normal and nothing to worry about.
