Hypertonic saline is any salt-water solution with a higher concentration than your body’s natural fluids. To make a 3% hypertonic saline solution, you dissolve 30 grams of non-iodized salt in 1 liter of distilled or sterilized water. That ratio, confirmed by the FDA’s laboratory preparation standards, is the most commonly referenced concentration for home and clinical use.
The process itself is simple, but getting the concentration right and keeping the solution sterile are what separate a useful preparation from a potentially harmful one. Here’s how to do it safely.
What Makes Saline “Hypertonic”
Normal saline, the kind used in IV bags and basic nasal rinses, is 0.9% sodium chloride. It matches the salt concentration of your blood and tissues. Hypertonic saline is saltier than that, typically 3% or 7%, which means it pulls water out of swollen tissues through osmosis. That’s why it’s used to thin thick mucus in the lungs, reduce tissue swelling, and clear congested sinuses more aggressively than a standard saline rinse.
A 3% solution is the most common concentration prepared at home. Higher concentrations like 7% are used in clinical settings, particularly for people with cystic fibrosis, and are best obtained as sterile, pre-packaged vials rather than mixed at home.
Ingredients You Need
You only need two things: salt and water. But the type of each matters.
- Salt: Use non-iodized salt with no additives. Table salt often contains anti-caking agents and iodine, both of which can irritate tissues. Pickling salt, canning salt, or pharmaceutical-grade sodium chloride are better choices. Check the label to confirm sodium chloride is the only ingredient.
- Water: Distilled water is the safest option. If you don’t have distilled water, you can sterilize tap water by boiling it (details below). Never use unboiled tap water for any solution that will contact your nasal passages, lungs, or open wounds.
Some recipes for nasal irrigation call for adding 1 teaspoon of baking soda per batch to buffer the solution and reduce stinging. Cleveland Clinic includes baking soda in their recommended saline recipe for this reason. For a simple hypertonic solution, though, salt and water alone are sufficient.
Step-by-Step Preparation
For a 3% hypertonic saline solution:
- Measure 30 grams of non-iodized salt. If you don’t have a kitchen scale, 5 level teaspoons of table salt equals approximately 30 grams (each teaspoon of salt weighs about 6 grams).
- Prepare 1 liter of sterile water. If using distilled water, you can use it directly. If sterilizing tap water, bring it to a rolling boil for at least 10 minutes, then let it cool.
- Dissolve the salt completely. Add the salt to the warm (not boiling) water and stir until no crystals remain. Warm water dissolves salt faster, but let the solution cool to a comfortable temperature before use.
- Transfer to a clean container. Use a glass jar or bottle that has been washed with hot, soapy water and rinsed thoroughly. Sterilizing the container by boiling it for a few minutes adds an extra layer of safety.
If you’re on well water, the sterilization process is more involved. Boil the water for 10 minutes, let it cool for one hour, then boil it again for another 10 minutes before mixing. This double-boil method addresses contaminants that a single boil may not eliminate.
Scaling the Recipe
If you don’t need a full liter, scale down proportionally. For 500 milliliters (about 2 cups), use 15 grams of salt, which is 2.5 teaspoons. For 250 milliliters (1 cup), use 7.5 grams, or roughly 1ΒΌ teaspoons. A kitchen scale costing a few dollars will give you far more accurate results than measuring spoons, since salt crystal size varies between brands.
Storage and Shelf Life
Homemade saline does not last long. Store it in the refrigerator and discard any unused portion after three days, per UC Davis Health guidelines. Bacteria grow readily in salt water at room temperature, and homemade solutions lack the preservatives found in commercial products.
If your solution has been refrigerated, take out only the amount you need and let it warm to room temperature for about an hour before using it. Cold saline sprayed into your sinuses or nebulized into your lungs is uncomfortable and can trigger coughing or airway tightening.
Making smaller batches more frequently is generally better than preparing a large volume you won’t use within three days.
Common Uses for Hypertonic Saline
Most people making hypertonic saline at home fall into a few categories. Sinus sufferers use it in neti pots or squeeze bottles to flush out thick mucus more effectively than normal saline. The higher salt concentration draws more fluid out of swollen nasal tissue, which can provide relief during sinus infections or severe allergies.
People with cystic fibrosis or chronic lung conditions sometimes nebulize hypertonic saline to loosen airway mucus. Research has shown that inhaling hypertonic saline twice a day helps people with CF experience fewer lung infections, and it’s typically used before or during chest physiotherapy. The standard nebulized dose is about 4 milliliters per session. For nebulizer use specifically, sterile commercially prepared vials are strongly recommended over homemade solutions, since any bacterial contamination goes directly into the lungs.
Hypertonic saline also sees use in wound care, where it can help draw fluid out of edematous (swollen) tissue around a wound bed.
Side Effects and Precautions
The most common reactions to hypertonic saline are cough, throat irritation, and an unpleasant salty taste. In clinical trials of 7% hypertonic saline in children with cystic fibrosis, cough was the most frequently reported side effect, though it typically disappeared after the first use.
The more serious concern is bronchospasm, a sudden tightening of the airways. This risk is highest in people with asthma or reactive airway disease. In clinical settings, a bronchodilator is given before hypertonic saline inhalation to prevent this. If you have asthma or any history of airway reactivity, do not nebulize hypertonic saline without medical guidance.
Contamination is the other major risk with homemade solutions. Using non-sterile water in a nasal rinse can introduce dangerous organisms. Distilled or properly boiled water eliminates this risk. For nebulizer use, where the solution reaches deep into the lungs, the margin for error is even smaller, which is why the Cystic Fibrosis Foundation recommends sterile unit-dose formulations rather than homemade preparations for lung therapy.
How Concentration Affects Results
The difference between a 3% and 7% solution is not just saltiness. Higher concentrations pull more water from tissues, which means they’re more effective at thinning mucus but also more likely to cause irritation. If you’re new to hypertonic saline for sinus rinsing, starting at 2% to 3% and seeing how you tolerate it is a practical approach. You can adjust upward if needed.
Getting the concentration wrong in the other direction matters too. A solution that’s too dilute won’t have the osmotic effect you’re looking for. And a solution that’s far too concentrated, say 10% or above, can damage delicate mucosal tissue. Accurate measuring is worth the extra minute it takes.