Whether you take or skip a medication before dialysis depends entirely on the specific drug, and the answer is different for almost every pill in your regimen. There is no single blanket rule, despite a widespread practice of holding all blood pressure drugs on dialysis mornings. The reality is more granular: some medications are pulled out of your blood during the session and need a replacement dose afterward, some can cause dangerous drops in blood pressure if taken right before, and others need to be taken on schedule regardless. Getting this wrong in either direction carries real consequences.
The Blood Pressure Medication Question
Blood pressure drugs are the most debated category, and the one most likely to prompt the “hold or take?” conversation. A common practice in dialysis units is to tell patients to skip their morning antihypertensive on treatment days. The logic sounds reasonable: dialysis removes fluid, which lowers blood pressure on its own, so adding a blood pressure pill on top could cause a dangerous drop during the session. This drop, called intradialytic hypotension, can cause dizziness, cramping, nausea, and in serious cases, cardiac events.
But the evidence behind routine withholding is thinner than you might expect. A review of the available data concluded that withholding blood pressure medications before hemodialysis should not be a routine practice, noting that despite little evidence to support the recommendation, more than half of dialysis patients use some form of this method.1PubMed Central. Timing of blood pressure medications and intradialytic hypotension In other words, it became standard practice through habit rather than through strong clinical trials.
A cluster randomized trial directly tested this question by assigning patients to either take or hold their blood pressure medications before hemodialysis. The study could not show that taking medications was equivalent to holding them for the outcome of intradialytic hypotension, with a mean difference of about 8 percentage points between the two strategies.2PubMed Central. Timing of Antihypertensive Medications on Key Outcomes in Hemodialysis: A Cluster Randomized Trial That result is ambiguous enough that it did not settle the debate. What it did confirm is that the decision is not straightforward and likely should be individualized rather than applied as a blanket policy for everyone.
Not All Blood Pressure Drugs Carry the Same Risk
If you take multiple types of blood pressure medication, the class of drug matters. A study comparing different antihypertensive classes found that beta-blockers and alpha-beta blockers were associated with more than double the odds of intradialytic hypotension compared with calcium channel blockers. ACE inhibitors and ARBs also carried higher odds, and even diuretics showed an elevated risk compared with calcium channel blockers.3PubMed Central. Antihypertensive Drug Treatment and the Risk for Intrahemodialysis Hypotension
This has practical implications. If you are on a calcium channel blocker like amlodipine, your dialysis team may be more comfortable having you take it on schedule. If you are on a beta-blocker or an ACE inhibitor, the conversation about holding or adjusting the dose on dialysis days becomes more relevant. The decision should factor in your usual blood pressure readings, your history of drops during treatment, and the specific drugs you take.
Beta-Blockers and Dialysis Clearance
Beta-blockers deserve special attention because they are commonly prescribed in dialysis patients, and different beta-blockers behave very differently during a session. A randomized clinical trial measured how much of four common beta-blockers gets removed by hemodialysis. Atenolol and metoprolol were extensively cleared, with dialytic clearance values of 72 and 87 mL/min respectively using one measurement method. Carvedilol, by contrast, had a clearance of just 0.2 mL/min, meaning dialysis barely touched it.4PubMed Central. β-Blocker Dialyzability in Maintenance Hemodialysis Patients: A Randomized Clinical Trial
What this means for you: if you take atenolol or metoprolol, a significant chunk of the drug gets stripped out during dialysis. Your doctor may time your dose for after the session, or give you a supplemental dose, to keep the drug effective between treatments. If you take carvedilol, the session has almost no effect on your drug levels, so skipping it beforehand is less about it being removed and more about whether it contributes to blood pressure drops during treatment. Bisoprolol fell somewhere in the middle, with moderate clearance.
Diabetes Medications and the Hypoglycemia Trap
If you have diabetes and are on dialysis, blood sugar management gets tricky on treatment days. Dialysis itself can lower your blood sugar, even when the dialysis fluid contains glucose. Several factors contribute: the kidneys normally help produce glucose, and in kidney failure that source is diminished; insulin is cleared more slowly by damaged kidneys, so it hangs around longer; and dialysis can pull glucose from your blood into the machine’s fluid.5PubMed Central. Haemodialysis-induced hypoglycaemia and glycaemic disarrays
The risk of low blood sugar during or shortly after dialysis is real, and it is higher for people with diabetes than for those without. For this reason, insulin therapy and oral diabetes medications should be used carefully on dialysis days. Many clinicians recommend reducing the insulin dose before a session or taking diabetes pills after treatment instead of before. If you are on a sulfonylurea or a full dose of insulin, the combination with dialysis-induced glucose shifts can produce dangerously low readings. Talk to your nephrologist about a specific plan for dialysis days, because generic diabetes medication instructions were not designed with a four-hour hemodialysis session in mind.
Antibiotics and the Post-Session Dose
Antibiotics are one of the clearest examples of medications that need timing adjustments around dialysis. Many antibiotics are water-soluble and small enough to be pulled out during a session. Vancomycin, one of the most commonly used intravenous antibiotics in dialysis patients, illustrates why timing matters. When given during the last one to two hours of high-flux hemodialysis, vancomycin levels drop by roughly 25 to 35 percent. After the session ends, drug levels partially bounce back over three to six hours as the drug redistributes from tissue-binding sites. Because of this rebound effect, checking vancomycin levels right after dialysis gives a misleadingly low reading; monitoring is recommended before the next session instead.6PubMed Central. Post-Dialysis Parenteral Antimicrobial Therapy in Patients Receiving Intermittent High-Flux Hemodialysis – Section: Vancomycin
The general principle for dialyzable antibiotics is to give the dose after the session, so the drug stays in your system for the full interval between treatments. If you are prescribed an oral antibiotic and your pharmacist tells you to take it three times a day, that instruction might need adjustment on dialysis days. The dose that would normally go before the session may need to shift to after, and a supplemental dose may be needed. This is a conversation for your prescriber, but the key point is: do not assume your antibiotic schedule stays the same on dialysis days.
Anti-Seizure Medications
Levetiracetam, one of the most commonly prescribed anti-seizure drugs, is substantially removed by hemodialysis. Research in patients on intermittent hemodialysis supports the need for a supplemental dose after each session to prevent drug levels from falling below the effective range.7Journal of the Medical Association of Thailand. The Plasma Concentration Profiles and Pharmacokinetics of Levetiracetam among Thai Adult Patients Undergoing Intermittent Hemodialysis The same study cautioned that simply reducing the daily dose without accounting for dialysis losses would result in levels too low to prevent seizures. If you take levetiracetam, your doctor should have a specific plan for dosing on dialysis days, typically involving a top-up after each treatment.
Other anti-seizure medications vary in how much dialysis removes them. Phenytoin is heavily protein-bound, which generally means less removal, but its free (active) fraction increases in kidney disease, complicating things further. Gabapentin and pregabalin are both cleared significantly by dialysis and typically require supplemental dosing. The recurring theme: any anti-seizure drug you take needs its own dialysis-day plan, because missing a dose or having levels drop too low can have immediate and serious consequences.
Pain Medications and Drugs to Avoid
Pain management in dialysis patients is a minefield, and the stakes of getting it wrong go beyond inadequate pain relief. Morphine and codeine are explicitly not recommended for dialysis patients because their breakdown products accumulate and can cause neurotoxic symptoms, including excessive sedation, confusion, and respiratory depression. Oxycodone and hydromorphone can be used more safely, though both need dose adjustments.8Therapeutics and Clinical Risk Management. Safe Use of Opioids in Chronic Kidney Disease and Hemodialysis Patients: Tips and Tricks for Non-Pain Specialists
This is not just a timing issue but an outright avoidance issue. If you are on dialysis and someone prescribes you codeine or morphine, that warrants a conversation with your nephrologist. The problem is not that dialysis removes these drugs too aggressively; it is that the kidneys normally clear their toxic metabolites, and in kidney failure, those metabolites build up between sessions regardless of when you take the dose.
Baclofen, a common muscle relaxant, is another drug that can cause serious toxicity in dialysis patients. A case report described a 74-year-old dialysis patient who developed depressed consciousness after receiving just 20 mg of baclofen for back pain. She required continuous hemodialysis sessions to clear the drug and recovered neurologically within two days.9PubMed Central. Baclofen Toxicity in a Dialysis-Dependent Patient: A Case Report A standard dose for someone with normal kidneys became a toxic dose for a dialysis patient. This is the kind of issue that falls through the cracks when a non-renal specialist prescribes a medication without checking kidney function.
Phosphate Binders Are Different From Most Medications
Phosphate binders (like sevelamer, calcium acetate, or lanthanum) work entirely inside the gut. They grab phosphorus from the food you eat and prevent it from being absorbed into your bloodstream. Because they are not absorbed into the blood themselves, dialysis does not remove them, and the question of “hold or take” does not apply in the usual sense. The real question is whether you eat during dialysis.
Many patients eat meals or snacks during their sessions. If you eat, you should take your phosphate binder with that food, just as you would at home. Skipping the binder because you are “at dialysis” defeats the purpose. Research has found that patients actually consume more phosphorus on dialysis days than on non-dialysis days, and patients with lower overall phosphorus intake were more likely to skip their binders.10PubMed Central. Daily dietary phosphorus intake variability and hemodialysis patient adherence to phosphate binder therapy The takeaway: if food goes in your mouth, the binder should go with it, dialysis day or not.
Anticoagulants and the Double-Anticoagulation Problem
If you take a blood thinner for atrial fibrillation or another condition, dialysis creates a unique situation. The dialysis machine itself typically requires anticoagulation to keep blood from clotting in the circuit, usually with heparin given during the session. That means you are getting two sources of blood thinning on treatment days: your oral anticoagulant and the intradialytic heparin.
From a pharmacological standpoint, patients already on an oral anticoagulant should need either no intradialytic heparin or only a low dose. Yet there is no widely validated protocol for how to adjust heparin dosing in patients already on blood thinners, and monitoring practices vary considerably between dialysis centers.11PubMed Central. Ten tips to manage oral anticoagulation in hemodialysis patients with atrial fibrillation The practical risk is bleeding, whether from excessive anticoagulation during the session or from vascular access sites that will not stop oozing afterward. If you take warfarin or a direct oral anticoagulant, make sure your dialysis unit knows, and ask whether your intradialytic heparin dose has been adjusted accordingly.
Vitamins and Supplements You Might Need After Sessions
Dialysis strips out more than just waste products. Water-soluble vitamins are small molecules that pass through dialysis membranes easily. A study measuring losses during a standard four-hour hemodiafiltration session found significant depletion of vitamins B1, B6, B9 (folate), and vitamin C, along with zinc.12PubMed Central. Water-Soluble Vitamins and Trace Elements Losses during On-Line Hemodiafiltration A systematic review reinforced that supplementation with thiamine and other water-soluble vitamins is particularly important for hemodialysis patients to offset these repeated losses.13PubMed Central. Demand for Water-Soluble Vitamins in a Group of Patients with CKD versus Interventions and Supplementation—A Systematic Review
Most dialysis patients are prescribed a renal-specific multivitamin (commonly called a “renal vitamin”) for this reason. The optimal time to take it is typically after dialysis, since taking it before means the session will remove a portion of what you just took. If you are not currently on a renal vitamin, bring it up with your care team. Fat-soluble vitamins like A, D, E, and K are a different story: they are stored in body fat and not efficiently removed by dialysis, so they follow different rules and can actually accumulate to toxic levels if supplemented without monitoring.
What Makes a Drug Dialyzable
Understanding a few basic drug properties helps explain why some medications are removed and others are not. Research examining 89 drugs found that the degree to which a drug binds to proteins in the blood, its volume of distribution (how widely it spreads through body tissues), and its molecular weight all correlated with how much dialysis removed it.14PubMed. Effect of plasma protein binding, volume of distribution and molecular weight on the fraction of drugs eliminated by hemodialysis In plain terms: drugs that float freely in the blood (rather than sticking to proteins), stay mostly in the bloodstream (rather than hiding in fat or muscle tissue), and are small molecules are the ones dialysis pulls out most easily.
That said, these three properties explained only about a quarter of the variation between drugs. Other factors, including membrane type, blood flow rate, and session length, also play a role. This is why you cannot simply look up a drug’s protein binding and predict what will happen. The carvedilol versus atenolol comparison from earlier is a good illustration: both are beta-blockers, but their dialyzability could hardly be more different. Practical decisions still require drug-specific data, which is why dialysis pharmacists consult detailed tables rather than relying on rules of thumb.
Why Medication Reconciliation Matters So Much
Dialysis patients take an average of ten to twelve medications. Between multiple prescribers, changing doses, dialysis-day adjustments, and the sheer volume of pills, things fall through the cracks routinely. Formal medication reconciliation, where someone systematically reviews every drug a patient is taking and confirms the dose, timing, and appropriateness, has the potential to reduce medication-related problems, improve adherence, and lower costs.15PubMed Central. Medication Reconciliation: The Foundation of Medication Safety for Patients Requiring Dialysis
The most dangerous gaps tend to occur at transitions: a hospital discharge, a new prescription from a specialist who does not know your dialysis schedule, or a dose change that nobody communicated to the dialysis unit. Keeping an updated medication list, including the specific instructions for dialysis days versus non-dialysis days, is one of the most protective things you can do. If you are unsure about any medication’s timing, your dialysis pharmacist is often the best person to ask. They deal with these drug-specific questions every day and have access to the clearance data that determines whether a drug needs holding, supplementing, or neither.
Dialysis Modality Changes the Equation
Not all dialysis is the same, and the type of dialysis you receive affects how much medication gets removed. High-flux hemodialysis membranes clear drugs more aggressively than standard membranes. Hemodiafiltration, which combines diffusion and convection, removes even more. A case report comparing methotrexate clearance between high-flux hemodialysis and continuous peritoneal dialysis found that hemodialysis achieved higher time-averaged clearance than peritoneal dialysis.16PubMed Central. Methotrexate clearance by high-flux hemodialysis and peritoneal dialysis: a case report
If you are on peritoneal dialysis rather than hemodialysis, the drug removal profile is generally gentler and more continuous, since the treatment runs over many hours (or overnight) rather than concentrating clearance into a few-hour session. Medication timing adjustments are therefore less dramatic for peritoneal dialysis patients, though some drugs still require attention. Patients who switch from one modality to another should expect their medication plan to be reviewed and potentially restructured. The instructions you followed for in-center hemodialysis may not apply to home peritoneal dialysis, and vice versa.
Building Your Own Dialysis-Day Medication Plan
Given how individualized these decisions are, the most useful thing you can do is create a clear, written plan with your dialysis team. Organize your medications into three buckets:
- Take as usual: Drugs that are not affected by dialysis and do not contribute to intradialytic symptoms. Phosphate binders taken with meals, most statins, and many topical medications fall here.
- Hold before, take after: Drugs your team has specifically told you to skip on dialysis mornings. This often includes certain blood pressure medications and some diabetes medications. “After” typically means right after you get off the machine or when you get home.
- Supplement after: Drugs that dialysis removes significantly, requiring an extra dose post-session. Certain antibiotics, anti-seizure medications, and renal vitamins commonly belong here.
Write the plan down, keep a copy in your dialysis bag, and review it any time a medication is added or changed. The difference between a missed dose that does not matter and one that does can be hard to judge on your own, so lean on the people who know the pharmacology. Getting the timing right is one of the few aspects of dialysis you have direct control over, and it makes a measurable difference in how well your treatments work and how you feel during and after each session.